I'm looking for magical Java class that will allow me to do something like this:
ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
FileOutputStream fileStream = new FileOutputStream(new File("/tmp/somefile"));
MultiOutputStream outStream = new MultiOutputStream(byteStream, fileStream);
outStream.write("Hello world".getBytes());
Basically, I want tee for OutputStreams in Java. Any ideas?
Thanks!
Try the Apache Commons TeeOutputStream.
Just roll your own. There isn't any magic at all. Using Apache's TeeOutputStream you would basically use the code below. Of course using the Apache Commons I/O library you can leverage other classes, but sometimes it is nice to actually write something for yourself. :)
public final class TeeOutputStream extends OutputStream {
private final OutputStream out;
private final OutputStream tee;
public TeeOutputStream(OutputStream out, OutputStream tee) {
if (out == null)
throw new NullPointerException();
else if (tee == null)
throw new NullPointerException();
this.out = out;
this.tee = tee;
}
#Override
public void write(int b) throws IOException {
out.write(b);
tee.write(b);
}
#Override
public void write(byte[] b) throws IOException {
out.write(b);
tee.write(b);
}
#Override
public void write(byte[] b, int off, int len) throws IOException {
out.write(b, off, len);
tee.write(b, off, len);
}
#Override
public void flush() throws IOException {
out.flush();
tee.flush();
}
#Override
public void close() throws IOException {
try {
out.close();
} finally {
tee.close();
}
}
}
Testing with the above class with the following
public static void main(String[] args) throws IOException {
TeeOutputStream out = new TeeOutputStream(System.out, System.out);
out.write("Hello world!".getBytes());
out.flush();
out.close();
}
would print Hello World!Hello World!.
(Note: the overridden close() could use some care tho' :)
Just found this thread beacause I had to face the same problem.
If someone wants to see my solution (java7 code):
package Core;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class MultiOutputStream extends OutputStream {
private List<OutputStream> out;
public MultiOutputStream(List<OutputStream> outStreams) {
this.out = new LinkedList<OutputStream>();
for (Iterator<OutputStream> i = outStreams.iterator(); i.hasNext();) {
OutputStream outputStream = (OutputStream) i.next();
if(outputStream == null){
throw new NullPointerException();
}
this.out.add(outputStream);
}
}
#Override
public void write(int arg0) throws IOException {
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(arg0);
}
}
#Override
public void write(byte[] b) throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(b);
}
}
#Override
public void write(byte[] b, int off, int len) throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(b, off, len);
}
}
#Override
public void close() throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.close();
}
}
#Override
public void flush() throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.flush();
}
}
}
Works fine so far, just tested some basic operation, e.g. setting up a MultiOutputStream from the System.out Stream and 2 PrintStreams each writing into a seperate log.
I used
System.setOut(multiOutputStream);
to write to my terminal screen and two logs which worked without any problems.
final ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
final FileOutputStream fileStream = new FileOutputStream(new File("/tmp/somefile"));
OutputStream outStream = new OutputStream() {
public void write(int b) throws IOException {
byteStream.write(b);
fileStream.write(b);
}
};
outStream.write("Hello world".getBytes());
Roll your own, it's basically trivial. Use an ArrayList<OutputStream> or whatever's popular nowadays to store all the streams you want and write the write method to loop over all of them, writing to each.
I'm not a Java expert, but I know the basics of Java and I always try to understand Java code in depth always whenever it come across.
It could be a really silly doubt but would love to make it clear understanding in my mind.
I'm posting in the Java community, because my doubt is about Java only.
Since the last couple of months I am working with hadoop and came across that hadoop uses its own types, which are wrapped around Java's primitive types in order to increase efficiency to send data across network on the basis of serialization and deserialization.
My confusion starts from here, Lets say we have some data in HDFS to be processed using following Java code running in hadoop code
org.apache.hadoop.io.IntWritable;
org.apache.hadoop.io.LongWritable;
org.apache.hadoop.io.Text;
org.apache.hadoop.mapreduce.Mapper;
import java.io.IOException;
public class WordCountMapper
{
extends Mapper<LongWritable,Text,Text,IntWritable>
#Override
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException{
}
}
String line = value.toString();
for (String word : line.split(" ")){
if(word.length()>0){
context.write(new Text(word),new IntWritable(1));
}
In this code hadoop's types are like this LongWritable, Text, IntWritable.
Lets pick up Text type which is wrapped around String type of Java (correct me if am wrong).
My doubt here is when we are passing these parameters to our method map in the above code, how these parameters gets interact with the code which is in import package i.e org.apache.hadoop.io.Text;
Below is the Text class code
package org.apache.hadoop.io;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CodingErrorAction;
import java.nio.charset.MalformedInputException;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.Arrays;
import org.apache.avro.reflect.Stringable;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Stable;
#Stringable
#InterfaceAudience.Public
#InterfaceStability.Stable
public class Text
extends BinaryComparable
implements WritableComparable<BinaryComparable>
{
private static final Log LOG = LogFactory.getLog(Text.class);
private static ThreadLocal<CharsetEncoder> ENCODER_FACTORY = new ThreadLocal()
{
protected CharsetEncoder initialValue() {
return Charset.forName("UTF-8").newEncoder().onMalformedInput(CodingErrorAction.REPORT).onUnmappableCharacter(CodingErrorAction.REPORT);
}
};
private static ThreadLocal<CharsetDecoder> DECODER_FACTORY = new ThreadLocal()
{
protected CharsetDecoder initialValue() {
return Charset.forName("UTF-8").newDecoder().onMalformedInput(CodingErrorAction.REPORT).onUnmappableCharacter(CodingErrorAction.REPORT);
}
};
private static final byte[] EMPTY_BYTES = new byte[0];
private byte[] bytes;
private int length;
public Text()
{
bytes = EMPTY_BYTES;
}
public Text(String string)
{
set(string);
}
public Text(Text utf8)
{
set(utf8);
}
public Text(byte[] utf8)
{
set(utf8);
}
public byte[] getBytes()
{
return bytes;
}
public int getLength()
{
return length;
}
public int charAt(int position)
{
if (position > length) return -1;
if (position < 0) { return -1;
}
ByteBuffer bb = (ByteBuffer)ByteBuffer.wrap(bytes).position(position);
return bytesToCodePoint(bb.slice());
}
public int find(String what) {
return find(what, 0);
}
public int find(String what, int start)
{
try
{
ByteBuffer src = ByteBuffer.wrap(bytes, 0, length);
ByteBuffer tgt = encode(what);
byte b = tgt.get();
src.position(start);
while (src.hasRemaining()) {
if (b == src.get()) {
src.mark();
tgt.mark();
boolean found = true;
int pos = src.position() - 1;
while (tgt.hasRemaining()) {
if (!src.hasRemaining()) {
tgt.reset();
src.reset();
found = false;
}
else if (tgt.get() != src.get()) {
tgt.reset();
src.reset();
found = false;
}
}
if (found) return pos;
}
}
return -1;
}
catch (CharacterCodingException e) {
e.printStackTrace(); }
return -1;
}
public void set(String string)
{
try
{
ByteBuffer bb = encode(string, true);
bytes = bb.array();
length = bb.limit();
} catch (CharacterCodingException e) {
throw new RuntimeException("Should not have happened " + e.toString());
}
}
public void set(byte[] utf8)
{
set(utf8, 0, utf8.length);
}
public void set(Text other)
{
set(other.getBytes(), 0, other.getLength());
}
public void set(byte[] utf8, int start, int len)
{
setCapacity(len, false);
System.arraycopy(utf8, start, bytes, 0, len);
length = len;
}
public void append(byte[] utf8, int start, int len)
{
setCapacity(length + len, true);
System.arraycopy(utf8, start, bytes, length, len);
length += len;
}
public void clear()
{
length = 0;
}
private void setCapacity(int len, boolean keepData)
{
if ((bytes == null) || (bytes.length < len)) {
if ((bytes != null) && (keepData)) {
bytes = Arrays.copyOf(bytes, Math.max(len, length << 1));
} else {
bytes = new byte[len];
}
}
}
public String toString()
{
try
{
return decode(bytes, 0, length);
} catch (CharacterCodingException e) {
throw new RuntimeException("Should not have happened " + e.toString());
}
}
public void readFields(DataInput in)
throws IOException
{
int newLength = WritableUtils.readVInt(in);
setCapacity(newLength, false);
in.readFully(bytes, 0, newLength);
length = newLength;
}
public static void skip(DataInput in) throws IOException
{
int length = WritableUtils.readVInt(in);
WritableUtils.skipFully(in, length);
}
public void write(DataOutput out)
throws IOException
{
WritableUtils.writeVInt(out, length);
out.write(bytes, 0, length);
}
public boolean equals(Object o)
{
if ((o instanceof Text))
return super.equals(o);
return false;
}
May I know please when ever we run the above hadoop's code, data in HDFS flows across the parameters we have mentioned in the map method.
Once the first data set from HDFS hits the Text parameter how it flows inside the org.apache.hadoop.io.Text class?
I mean from where does it start (I'm assuming it's starting from set method in class because it has kind of same parameters as mentioned map method, am I correct?)
Where does it change from normal string type to Text type in code?
My Second doubt is: when data is stored in Text type, then who kicks it to start doing serilzation? I mean who calls this write(DataOutput out), and who calls readFields(DataInput in) once data is reached to its destination on network?
How does it work, and where do I need to look?
I hope what I am asking is clear.
Like all network or disk operations, everything is transferred as bytes. The Text class deserializes bytes to UTF-8. The Writables determine how data is represented and Comparables determine how data is ordered.
The InputFormat set in the Job determines what Writables are given to a map or reduce Task.
An InputSplit determines how to split and read a raw byte stream into the Writables
One map task is started on each InputSplit
Refer https://hadoop.apache.org/docs/stable/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduceTutorial.html
I want to read the last output from the console and then save it to a variable.
Let's say I have this code and output:
System.out.println("first");
System.out.println("second");
System.out.println("third");
...
**...THE CODE HERE...**
first
second
third
Now I want it to read the last/latest output from the console and save it to a variable/string.
Any ideas?
The task is quite strange, but here's quick-and-dirty solution:
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.StringWriter;
public class FilterOutput {
static class MemorizingOutputStream extends FilterOutputStream {
StringWriter sw = new StringWriter();
String last = null;
public MemorizingOutputStream(OutputStream out) {
super(out);
}
#Override
public void write(int b) throws IOException {
write(new byte[] {(byte)b}, 0, 1);
}
#Override
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
#Override
public void write(byte[] b, int off, int len) throws IOException {
out.write(b, off, len);
String s = new String(b, off, len);
int pos = s.lastIndexOf('\n');
if(pos == -1) {
sw.append(s);
} else {
int pos2 = s.lastIndexOf('\n', pos-1);
if(pos2 == -1) {
sw.append(s.substring(0, pos));
last = sw.toString();
} else {
last = s.substring(pos2+1, pos);
}
sw = new StringWriter();
sw.append(s.substring(pos+1));
}
}
public String getLast() {
return last;
}
}
public static void main(String[] args) {
MemorizingOutputStream memOut = new MemorizingOutputStream(System.out);
System.setOut(new PrintStream(memOut));
System.out.println("first");
System.out.println("second");
System.out.println("third");
System.err.println(memOut.getLast());
}
}
First it replaces the standard output stream with special stream which memorizes the last string (assuming that strings end with '\n'). Then you can query that stream for the last string which was printed. Note that this implementation is not thread-safe.
I'm trying to access two http request parameters in a Java Servlet filter, nothing new here, but was surprised to find that the parameters have already been consumed! Because of this, they are not available in the filter chain anymore.
It seems that this only occurs when parameters come in a POST request body (a form submit, for example).
Is there a way to read the parameters and NOT consume them?
So far I've found only this reference: Servlet Filter using request.getParameter loses Form data.
Thanks!
As an aside, an alternative way to solve this problem is to not use the filter chain and instead build your own interceptor component, perhaps using aspects, which can operate on the parsed request body. It will also likely be more efficient as you are only converting the request InputStream into your own model object once.
However, I still think it's reasonable to want to read the request body more than once particularly as the request moves through the filter chain. I would typically use filter chains for certain operations that I want to keep at the HTTP layer, decoupled from the service components.
As suggested by Will Hartung I achieved this by extending HttpServletRequestWrapper, consuming the request InputStream and essentially caching the bytes.
public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
private ByteArrayOutputStream cachedBytes;
public MultiReadHttpServletRequest(HttpServletRequest request) {
super(request);
}
#Override
public ServletInputStream getInputStream() throws IOException {
if (cachedBytes == null)
cacheInputStream();
return new CachedServletInputStream();
}
#Override
public BufferedReader getReader() throws IOException{
return new BufferedReader(new InputStreamReader(getInputStream()));
}
private void cacheInputStream() throws IOException {
/* Cache the inputstream in order to read it multiple times. For
* convenience, I use apache.commons IOUtils
*/
cachedBytes = new ByteArrayOutputStream();
IOUtils.copy(super.getInputStream(), cachedBytes);
}
/* An input stream which reads the cached request body */
private static class CachedServletInputStream extends ServletInputStream {
private final ByteArrayInputStream buffer;
public CachedServletInputStream(byte[] contents) {
this.buffer = new ByteArrayInputStream(contents);
}
#Override
public int read() {
return buffer.read();
}
#Override
public boolean isFinished() {
return buffer.available() == 0;
}
#Override
public boolean isReady() {
return true;
}
#Override
public void setReadListener(ReadListener listener) {
throw new RuntimeException("Not implemented");
}
}
}
Now the request body can be read more than once by wrapping the original request before passing it through the filter chain:
public class MyFilter implements Filter {
#Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
/* wrap the request in order to read the inputstream multiple times */
MultiReadHttpServletRequest multiReadRequest = new MultiReadHttpServletRequest((HttpServletRequest) request);
/* here I read the inputstream and do my thing with it; when I pass the
* wrapped request through the filter chain, the rest of the filters, and
* request handlers may read the cached inputstream
*/
doMyThing(multiReadRequest.getInputStream());
//OR
anotherUsage(multiReadRequest.getReader());
chain.doFilter(multiReadRequest, response);
}
}
This solution will also allow you to read the request body multiple times via the getParameterXXX methods because the underlying call is getInputStream(), which will of course read the cached request InputStream.
Edit
For newer version of ServletInputStream interface. You need to provide implementation of few more methods like isReady, setReadListener etc. Refer this question as provided in comment below.
I know I'm late, but this question was still relevant for me and this SO post was one of the top hits in Google. I'm going ahead and post my solution in the hopes that someone else might save couple of hours.
In my case I needed to log all requests and responses with their bodies. Using Spring Framework the answer is actually quite simple, just use ContentCachingRequestWrapper and ContentCachingResponseWrapper.
import org.springframework.web.util.ContentCachingRequestWrapper;
import org.springframework.web.util.ContentCachingResponseWrapper;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoggingFilter implements Filter {
#Override
public void init(FilterConfig filterConfig) throws ServletException {
}
#Override
public void destroy() {
}
#Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper((HttpServletRequest) request);
ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper((HttpServletResponse) response);
try {
chain.doFilter(requestWrapper, responseWrapper);
} finally {
String requestBody = new String(requestWrapper.getContentAsByteArray());
String responseBody = new String(responseWrapper.getContentAsByteArray());
// Do not forget this line after reading response content or actual response will be empty!
responseWrapper.copyBodyToResponse();
// Write request and response body, headers, timestamps etc. to log files
}
}
}
The above answers were very helpful, but still had some problems in my experience. On tomcat 7 servlet 3.0, the getParamter and getParamterValues also had to be overwritten. The solution here includes both get-query parameters and the post-body. It allows for getting raw-string easily.
Like the other solutions it uses Apache commons-io and Googles Guava.
In this solution the getParameter* methods do not throw IOException but they use super.getInputStream() (to get the body) which may throw IOException. I catch it and throw runtimeException. It is not so nice.
import com.google.common.collect.Iterables;
import com.google.common.collect.ObjectArrays;
import org.apache.commons.io.IOUtils;
import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.entity.ContentType;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
/**
* Purpose of this class is to make getParameter() return post data AND also be able to get entire
* body-string. In native implementation any of those two works, but not both together.
*/
public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
public static final String UTF8 = "UTF-8";
public static final Charset UTF8_CHARSET = Charset.forName(UTF8);
private ByteArrayOutputStream cachedBytes;
private Map<String, String[]> parameterMap;
public MultiReadHttpServletRequest(HttpServletRequest request) {
super(request);
}
public static void toMap(Iterable<NameValuePair> inputParams, Map<String, String[]> toMap) {
for (NameValuePair e : inputParams) {
String key = e.getName();
String value = e.getValue();
if (toMap.containsKey(key)) {
String[] newValue = ObjectArrays.concat(toMap.get(key), value);
toMap.remove(key);
toMap.put(key, newValue);
} else {
toMap.put(key, new String[]{value});
}
}
}
#Override
public ServletInputStream getInputStream() throws IOException {
if (cachedBytes == null) cacheInputStream();
return new CachedServletInputStream();
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(getInputStream()));
}
private void cacheInputStream() throws IOException {
/* Cache the inputStream in order to read it multiple times. For
* convenience, I use apache.commons IOUtils
*/
cachedBytes = new ByteArrayOutputStream();
IOUtils.copy(super.getInputStream(), cachedBytes);
}
#Override
public String getParameter(String key) {
Map<String, String[]> parameterMap = getParameterMap();
String[] values = parameterMap.get(key);
return values != null && values.length > 0 ? values[0] : null;
}
#Override
public String[] getParameterValues(String key) {
Map<String, String[]> parameterMap = getParameterMap();
return parameterMap.get(key);
}
#Override
public Map<String, String[]> getParameterMap() {
if (parameterMap == null) {
Map<String, String[]> result = new LinkedHashMap<String, String[]>();
decode(getQueryString(), result);
decode(getPostBodyAsString(), result);
parameterMap = Collections.unmodifiableMap(result);
}
return parameterMap;
}
private void decode(String queryString, Map<String, String[]> result) {
if (queryString != null) toMap(decodeParams(queryString), result);
}
private Iterable<NameValuePair> decodeParams(String body) {
Iterable<NameValuePair> params = URLEncodedUtils.parse(body, UTF8_CHARSET);
try {
String cts = getContentType();
if (cts != null) {
ContentType ct = ContentType.parse(cts);
if (ct.getMimeType().equals(ContentType.APPLICATION_FORM_URLENCODED.getMimeType())) {
List<NameValuePair> postParams = URLEncodedUtils.parse(IOUtils.toString(getReader()), UTF8_CHARSET);
params = Iterables.concat(params, postParams);
}
}
} catch (IOException e) {
throw new IllegalStateException(e);
}
return params;
}
public String getPostBodyAsString() {
try {
if (cachedBytes == null) cacheInputStream();
return cachedBytes.toString(UTF8);
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/* An inputStream which reads the cached request body */
public class CachedServletInputStream extends ServletInputStream {
private ByteArrayInputStream input;
public CachedServletInputStream() {
/* create a new input stream from the cached request body */
input = new ByteArrayInputStream(cachedBytes.toByteArray());
}
#Override
public int read() throws IOException {
return input.read();
}
}
#Override
public String toString() {
String query = dk.bnr.util.StringUtil.nullToEmpty(getQueryString());
StringBuilder sb = new StringBuilder();
sb.append("URL='").append(getRequestURI()).append(query.isEmpty() ? "" : "?" + query).append("', body='");
sb.append(getPostBodyAsString());
sb.append("'");
return sb.toString();
}
}
So this is basically Lathy's answer BUT updated for newer requirements for ServletInputStream.
Namely (for ServletInputStream), one has to implement:
public abstract boolean isFinished();
public abstract boolean isReady();
public abstract void setReadListener(ReadListener var1);
This is the edited Lathy's object
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
public class RequestWrapper extends HttpServletRequestWrapper {
private String _body;
public RequestWrapper(HttpServletRequest request) throws IOException {
super(request);
_body = "";
BufferedReader bufferedReader = request.getReader();
String line;
while ((line = bufferedReader.readLine()) != null){
_body += line;
}
}
#Override
public ServletInputStream getInputStream() throws IOException {
CustomServletInputStream kid = new CustomServletInputStream(_body.getBytes());
return kid;
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream()));
}
}
and somewhere (??) I found this (which is a first-class class that deals with the "extra" methods.
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
public class CustomServletInputStream extends ServletInputStream {
private byte[] myBytes;
private int lastIndexRetrieved = -1;
private ReadListener readListener = null;
public CustomServletInputStream(String s) {
try {
this.myBytes = s.getBytes("UTF-8");
} catch (UnsupportedEncodingException ex) {
throw new IllegalStateException("JVM did not support UTF-8", ex);
}
}
public CustomServletInputStream(byte[] inputBytes) {
this.myBytes = inputBytes;
}
#Override
public boolean isFinished() {
return (lastIndexRetrieved == myBytes.length - 1);
}
#Override
public boolean isReady() {
// This implementation will never block
// We also never need to call the readListener from this method, as this method will never return false
return isFinished();
}
#Override
public void setReadListener(ReadListener readListener) {
this.readListener = readListener;
if (!isFinished()) {
try {
readListener.onDataAvailable();
} catch (IOException e) {
readListener.onError(e);
}
} else {
try {
readListener.onAllDataRead();
} catch (IOException e) {
readListener.onError(e);
}
}
}
#Override
public int read() throws IOException {
int i;
if (!isFinished()) {
i = myBytes[lastIndexRetrieved + 1];
lastIndexRetrieved++;
if (isFinished() && (readListener != null)) {
try {
readListener.onAllDataRead();
} catch (IOException ex) {
readListener.onError(ex);
throw ex;
}
}
return i;
} else {
return -1;
}
}
};
Ultimately, I was just trying to log the requests. And the above frankensteined together pieces helped me create the below.
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.Principal;
import java.util.Enumeration;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.io.IOUtils;
//one or the other based on spring version
//import org.springframework.boot.autoconfigure.web.ErrorAttributes;
import org.springframework.boot.web.servlet.error.ErrorAttributes;
import org.springframework.core.Ordered;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.filter.OncePerRequestFilter;
/**
* A filter which logs web requests that lead to an error in the system.
*/
#Component
public class LogRequestFilter extends OncePerRequestFilter implements Ordered {
// I tried apache.commons and slf4g loggers. (one or the other in these next 2 lines of declaration */
//private final static org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory.getLog(LogRequestFilter.class);
private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(LogRequestFilter.class);
// put filter at the end of all other filters to make sure we are processing after all others
private int order = Ordered.LOWEST_PRECEDENCE - 8;
private ErrorAttributes errorAttributes;
#Override
public int getOrder() {
return order;
}
#Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
String temp = ""; /* for a breakpoint, remove for production/real code */
/* change to true for easy way to comment out this code, remove this if-check for production/real code */
if (false) {
filterChain.doFilter(request, response);
return;
}
/* make a "copy" to avoid issues with body-can-only-read-once issues */
RequestWrapper reqWrapper = new RequestWrapper(request);
int status = HttpStatus.INTERNAL_SERVER_ERROR.value();
// pass through filter chain to do the actual request handling
filterChain.doFilter(reqWrapper, response);
status = response.getStatus();
try {
Map<String, Object> traceMap = getTrace(reqWrapper, status);
// body can only be read after the actual request handling was done!
this.getBodyFromTheRequestCopy(reqWrapper, traceMap);
/* now do something with all the pieces of information gatherered */
this.logTrace(reqWrapper, traceMap);
} catch (Exception ex) {
logger.error("LogRequestFilter FAILED: " + ex.getMessage(), ex);
}
}
private void getBodyFromTheRequestCopy(RequestWrapper rw, Map<String, Object> trace) {
try {
if (rw != null) {
byte[] buf = IOUtils.toByteArray(rw.getInputStream());
//byte[] buf = rw.getInputStream();
if (buf.length > 0) {
String payloadSlimmed;
try {
String payload = new String(buf, 0, buf.length, rw.getCharacterEncoding());
payloadSlimmed = payload.trim().replaceAll(" +", " ");
} catch (UnsupportedEncodingException ex) {
payloadSlimmed = "[unknown]";
}
trace.put("body", payloadSlimmed);
}
}
} catch (IOException ioex) {
trace.put("body", "EXCEPTION: " + ioex.getMessage());
}
}
private void logTrace(HttpServletRequest request, Map<String, Object> trace) {
Object method = trace.get("method");
Object path = trace.get("path");
Object statusCode = trace.get("statusCode");
logger.info(String.format("%s %s produced an status code '%s'. Trace: '%s'", method, path, statusCode,
trace));
}
protected Map<String, Object> getTrace(HttpServletRequest request, int status) {
Throwable exception = (Throwable) request.getAttribute("javax.servlet.error.exception");
Principal principal = request.getUserPrincipal();
Map<String, Object> trace = new LinkedHashMap<String, Object>();
trace.put("method", request.getMethod());
trace.put("path", request.getRequestURI());
if (null != principal) {
trace.put("principal", principal.getName());
}
trace.put("query", request.getQueryString());
trace.put("statusCode", status);
Enumeration headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
String key = (String) headerNames.nextElement();
String value = request.getHeader(key);
trace.put("header:" + key, value);
}
if (exception != null && this.errorAttributes != null) {
trace.put("error", this.errorAttributes
.getErrorAttributes((WebRequest) new ServletRequestAttributes(request), true));
}
return trace;
}
}
Please take this code with a grain of salt.
The MOST important "test" is if a POST works with a payload. This is what will expose "double read" issues.
pseudo example code
import org.springframework.web.bind.annotation.*;
#RestController
#RequestMapping("myroute")
public class MyController {
#RequestMapping(method = RequestMethod.POST, produces = "application/json")
#ResponseBody
public String getSomethingExample(#RequestBody MyCustomObject input) {
String returnValue = "";
return returnValue;
}
}
You can replace "MyCustomObject" with plain ole "Object" if you just want to test.
This answer is frankensteined from several different SOF posts and examples..but it took a while to pull it all together so I hope it helps a future reader.
Please upvote Lathy's answer before mine. I could have not gotten this far without it.
Below is one/some of the exceptions I got while working this out.
getReader() has already been called for this request
Looks like some of the places I "borrowed" from are here:
http://slackspace.de/articles/log-request-body-with-spring-boot/
https://github.com/c0nscience/spring-web-logging/blob/master/src/main/java/org/zalando/springframework/web/logging/LoggingFilter.java
https://howtodoinjava.com/servlets/httpservletrequestwrapper-example-read-request-body/
https://www.oodlestechnologies.com/blogs/How-to-create-duplicate-object-of-httpServletRequest-object
https://github.com/c0nscience/spring-web-logging/blob/master/src/main/java/org/zalando/springframework/web/logging/LoggingFilter.java
January 2021 APPEND.
I have learned the hard way that the above code does NOT work for
x-www-form-urlencoded
Consider the example below:
#CrossOrigin
#ResponseBody
#PostMapping(path = "/mypath", consumes = {MediaType.APPLICATION_FORM_URLENCODED_VALUE})
public ResponseEntity myMethodName(#RequestParam Map<String, String> parameters
) {
/* DO YOU GET ANY PARAMETERS HERE? Or are they empty because of logging/auditing filter ?*/
return new ResponseEntity(HttpStatus.OK);
}
I had to go through several of the other examples here.
I came up with a "wrapper" that works explicitly for APPLICATION_FORM_URLENCODED_VALUE
import org.apache.commons.io.IOUtils;
import org.springframework.http.MediaType;
import org.springframework.web.util.ContentCachingRequestWrapper;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
/**
* Makes a "copy" of the HttpRequest so the body can be accessed more than 1 time.
* WORKS WITH APPLICATION_FORM_URLENCODED_VALUE
* See : https://stackoverflow.com/questions/44182370/why-do-we-wrap-httpservletrequest-the-api-provides-an-httpservletrequestwrappe/44187955#44187955
*/
public final class AppFormUrlEncodedSpecificContentCachingRequestWrapper extends ContentCachingRequestWrapper {
public static final String ERROR_MSG_CONTENT_TYPE_NOT_SUPPORTED = "ContentType not supported. (Input ContentType(s)=\"%1$s\", Supported ContentType(s)=\"%2$s\")";
public static final String ERROR_MSG_PERSISTED_CONTENT_CACHING_REQUEST_WRAPPER_CONSTRUCTOR_FAILED = "AppFormUrlEncodedSpecificContentCachingRequestWrapper constructor failed";
private static final org.slf4j.Logger LOGGER = org.slf4j.LoggerFactory.getLogger(AppFormUrlEncodedSpecificContentCachingRequestWrapper.class);
private byte[] body;
private ServletInputStream inputStream;
public AppFormUrlEncodedSpecificContentCachingRequestWrapper(HttpServletRequest request) {
super(request);
super.getParameterMap(); // init cache in ContentCachingRequestWrapper. THIS IS THE VITAL CALL so that "#RequestParam Map<String, String> parameters" are populated on the REST Controller. See https://stackoverflow.com/questions/10210645/http-servlet-request-lose-params-from-post-body-after-read-it-once/64924380#64924380
String contentType = request.getContentType();
/* EXPLICTLY check for APPLICATION_FORM_URLENCODED_VALUE and allow nothing else */
if (null == contentType || !contentType.equalsIgnoreCase(MediaType.APPLICATION_FORM_URLENCODED_VALUE)) {
IllegalArgumentException ioex = new IllegalArgumentException(String.format(ERROR_MSG_CONTENT_TYPE_NOT_SUPPORTED, contentType, MediaType.APPLICATION_FORM_URLENCODED_VALUE));
LOGGER.error(ERROR_MSG_PERSISTED_CONTENT_CACHING_REQUEST_WRAPPER_CONSTRUCTOR_FAILED, ioex);
throw ioex;
}
try {
loadBody(request);
} catch (IOException ioex) {
throw new RuntimeException(ioex);
}
}
private void loadBody(HttpServletRequest request) throws IOException {
body = IOUtils.toByteArray(request.getInputStream());
inputStream = new CustomServletInputStream(this.getBody());
}
private byte[] getBody() {
return body;
}
#Override
public ServletInputStream getInputStream() throws IOException {
if (inputStream != null) {
return inputStream;
}
return super.getInputStream();
}
}
Note Andrew Sneck's answer on this same page.
It is pretty much this : https://programmersought.com/article/23981013626/
I have not had time to harmonize the two above implementations (my two that is).
So I created a Factory to "choose" from the two:
import org.springframework.http.MediaType;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.IOException;
/**
* Factory to return different concretes of HttpServletRequestWrapper. APPLICATION_FORM_URLENCODED_VALUE needs a different concrete.
*/
public class HttpServletRequestWrapperFactory {
public static final String ERROR_MSG_HTTP_SERVLET_REQUEST_WRAPPER_FACTORY_CREATE_HTTP_SERVLET_REQUEST_WRAPPER_FAILED = "HttpServletRequestWrapperFactory createHttpServletRequestWrapper FAILED";
public static HttpServletRequestWrapper createHttpServletRequestWrapper(final HttpServletRequest request) {
HttpServletRequestWrapper returnItem = null;
if (null != request) {
String contentType = request.getContentType();
if (null != contentType && contentType.equalsIgnoreCase(MediaType.APPLICATION_FORM_URLENCODED_VALUE)) {
returnItem = new AppFormUrlEncodedSpecificContentCachingRequestWrapper(request);
} else {
try {
returnItem = new PersistedBodyRequestWrapper(request);
} catch (IOException ioex) {
throw new RuntimeException(ERROR_MSG_HTTP_SERVLET_REQUEST_WRAPPER_FACTORY_CREATE_HTTP_SERVLET_REQUEST_WRAPPER_FAILED, ioex);
}
}
}
return returnItem;
}
}
Below is the "other" one that works with JSON, etc. It is the other concrete that the Factory can output. I put it here so that my Jan 2021 APPEND is consistent..I don't know if the code below is perfect consistent with my original answer:
import org.springframework.http.MediaType;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Map;
/**
* Makes a "copy" of the HttpRequest so the body can be accessed more than 1 time.
* See : https://stackoverflow.com/questions/44182370/why-do-we-wrap-httpservletrequest-the-api-provides-an-httpservletrequestwrappe/44187955#44187955
* DOES NOT WORK WITH APPLICATION_FORM_URLENCODED_VALUE
*/
public final class PersistedBodyRequestWrapper extends HttpServletRequestWrapper {
public static final String ERROR_MSG_CONTENT_TYPE_NOT_SUPPORTED = "ContentType not supported. (ContentType=\"%1$s\")";
public static final String ERROR_MSG_PERSISTED_BODY_REQUEST_WRAPPER_CONSTRUCTOR_FAILED = "PersistedBodyRequestWrapper constructor FAILED";
private static final org.slf4j.Logger LOGGER = org.slf4j.LoggerFactory.getLogger(PersistedBodyRequestWrapper.class);
private String persistedBody;
private final Map<String, String[]> parameterMap;
public PersistedBodyRequestWrapper(final HttpServletRequest request) throws IOException {
super(request);
String contentType = request.getContentType();
/* Allow everything EXCEPT APPLICATION_FORM_URLENCODED_VALUE */
if (null != contentType && contentType.equalsIgnoreCase(MediaType.APPLICATION_FORM_URLENCODED_VALUE)) {
IllegalArgumentException ioex = new IllegalArgumentException(String.format(ERROR_MSG_CONTENT_TYPE_NOT_SUPPORTED, MediaType.APPLICATION_FORM_URLENCODED_VALUE));
LOGGER.error(ERROR_MSG_PERSISTED_BODY_REQUEST_WRAPPER_CONSTRUCTOR_FAILED, ioex);
throw ioex;
}
parameterMap = request.getParameterMap();
this.persistedBody = "";
BufferedReader bufferedReader = request.getReader();
String line;
while ((line = bufferedReader.readLine()) != null) {
this.persistedBody += line;
}
}
#Override
public ServletInputStream getInputStream() throws IOException {
CustomServletInputStream csis = new CustomServletInputStream(this.persistedBody.getBytes(StandardCharsets.UTF_8));
return csis;
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream()));
}
#Override
public Map<String, String[]> getParameterMap() {
return this.parameterMap;
}
}
I found good solution for any format of request body.
I tested for application/x-www-form-urlencoded and application/json both worked very well. Problem of ContentCachingRequestWrapper that is designed only for x-www-form-urlencoded request body, but not work with e.g. json. I found solution for json link. It had trouble that it didn't support x-www-form-urlencoded.
I joined both in my code:
import org.apache.commons.io.IOUtils;
import org.springframework.web.util.ContentCachingRequestWrapper;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
public class MyContentCachingRequestWrapper extends ContentCachingRequestWrapper {
private byte[] body;
public MyContentCachingRequestWrapper(HttpServletRequest request) throws IOException {
super(request);
super.getParameterMap(); // init cache in ContentCachingRequestWrapper
body = super.getContentAsByteArray(); // first option for application/x-www-form-urlencoded
if (body.length == 0) {
try {
body = IOUtils.toByteArray(super.getInputStream()); // second option for other body formats
} catch (IOException ex) {
body = new byte[0];
}
}
}
public byte[] getBody() {
return body;
}
#Override
public ServletInputStream getInputStream() {
return new RequestCachingInputStream(body);
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(getInputStream(), getCharacterEncoding()));
}
private static class RequestCachingInputStream extends ServletInputStream {
private final ByteArrayInputStream inputStream;
public RequestCachingInputStream(byte[] bytes) {
inputStream = new ByteArrayInputStream(bytes);
}
#Override
public int read() throws IOException {
return inputStream.read();
}
#Override
public boolean isFinished() {
return inputStream.available() == 0;
}
#Override
public boolean isReady() {
return true;
}
#Override
public void setReadListener(ReadListener readlistener) {
}
}
}
The only way would be for you to consume the entire input stream yourself in the filter, take what you want from it, and then create a new InputStream for the content you read, and put that InputStream in to a ServletRequestWrapper (or HttpServletRequestWrapper).
The downside is you'll have to parse the payload yourself, the standard doesn't make that capability available to you.
Addenda --
As I said, you need to look at HttpServletRequestWrapper.
In a filter, you continue along by calling FilterChain.doFilter(request, response).
For trivial filters, the request and response are the same as the ones passed in to the filter. That doesn't have to be the case. You can replace those with your own requests and/or responses.
HttpServletRequestWrapper is specifically designed to facilitate this. You pass it the original request, and then you can intercept all of the calls. You create your own subclass of this, and replace the getInputStream method with one of your own. You can't change the input stream of the original request, so instead you have this wrapper and return your own input stream.
The simplest case is to consume the original requests input stream in to a byte buffer, do whatever magic you want on it, then create a new ByteArrayInputStream from that buffer. This is what is returned in your wrapper, which is passed to the FilterChain.doFilter method.
You'll need to subclass ServletInputStream and make another wrapper for your ByteArrayInputStream, but that's not a big deal either.
I too had the same issue and I believe the code below is more simple and it is working for me,
public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
private String _body;
public MultiReadHttpServletRequest(HttpServletRequest request) throws IOException {
super(request);
_body = "";
BufferedReader bufferedReader = request.getReader();
String line;
while ((line = bufferedReader.readLine()) != null){
_body += line;
}
}
#Override
public ServletInputStream getInputStream() throws IOException {
final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(_body.getBytes());
return new ServletInputStream() {
public int read() throws IOException {
return byteArrayInputStream.read();
}
};
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream()));
}
}
in the filter java class,
HttpServletRequest properRequest = ((HttpServletRequest) req);
MultiReadHttpServletRequest wrappedRequest = new MultiReadHttpServletRequest(properRequest);
req = wrappedRequest;
inputJson = IOUtils.toString(req.getReader());
System.out.println("body"+inputJson);
Please let me know if you have any queries
Spring has built-in support for this with an AbstractRequestLoggingFilter:
#Bean
public Filter loggingFilter(){
final AbstractRequestLoggingFilter filter = new AbstractRequestLoggingFilter() {
#Override
protected void beforeRequest(final HttpServletRequest request, final String message) {
}
#Override
protected void afterRequest(final HttpServletRequest request, final String message) {
}
};
filter.setIncludePayload(true);
filter.setIncludeQueryString(false);
filter.setMaxPayloadLength(1000000);
return filter;
}
Unfortunately you still won't be able to read the payload directly off the request, but the String message parameter will include the payload so you can grab it from there as follows:
String body = message.substring(message.indexOf("{"), message.lastIndexOf("]"));
Just overwriting of getInputStream() did not work in my case. My server implementation seems to parse parameters without calling this method. I did not find any other way, but re-implement the all four getParameter* methods as well. Here is the code of getParameterMap (Apache Http Client and Google Guava library used):
#Override
public Map<String, String[]> getParameterMap() {
Iterable<NameValuePair> params = URLEncodedUtils.parse(getQueryString(), NullUtils.UTF8);
try {
String cts = getContentType();
if (cts != null) {
ContentType ct = ContentType.parse(cts);
if (ct.getMimeType().equals(ContentType.APPLICATION_FORM_URLENCODED.getMimeType())) {
List<NameValuePair> postParams = URLEncodedUtils.parse(IOUtils.toString(getReader()), NullUtils.UTF8);
params = Iterables.concat(params, postParams);
}
}
} catch (IOException e) {
throw new IllegalStateException(e);
}
Map<String, String[]> result = toMap(params);
return result;
}
public static Map<String, String[]> toMap(Iterable<NameValuePair> body) {
Map<String, String[]> result = new LinkedHashMap<>();
for (NameValuePair e : body) {
String key = e.getName();
String value = e.getValue();
if (result.containsKey(key)) {
String[] newValue = ObjectArrays.concat(result.get(key), value);
result.remove(key);
result.put(key, newValue);
} else {
result.put(key, new String[] {value});
}
}
return result;
}
The method getContentAsByteArray() of the Spring class ContentCachingRequestWrapper reads the body multiple times, but the methods getInputStream() and getReader() of the same class do not read the body multiple times:
"This class caches the request body by consuming the InputStream. If we read the InputStream in one of the filters, then other subsequent filters in the filter chain can't read it anymore. Because of this limitation, this class is not suitable in all situations."
In my case more general solution that solved this problem was to add following three classes to my Spring boot project (and the required dependencies to the pom file):
CachedBodyHttpServletRequest.java:
public class CachedBodyHttpServletRequest extends HttpServletRequestWrapper {
private byte[] cachedBody;
public CachedBodyHttpServletRequest(HttpServletRequest request) throws IOException {
super(request);
InputStream requestInputStream = request.getInputStream();
this.cachedBody = StreamUtils.copyToByteArray(requestInputStream);
}
#Override
public ServletInputStream getInputStream() throws IOException {
return new CachedBodyServletInputStream(this.cachedBody);
}
#Override
public BufferedReader getReader() throws IOException {
// Create a reader from cachedContent
// and return it
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(this.cachedBody);
return new BufferedReader(new InputStreamReader(byteArrayInputStream));
}
}
CachedBodyServletInputStream.java:
public class CachedBodyServletInputStream extends ServletInputStream {
private InputStream cachedBodyInputStream;
public CachedBodyServletInputStream(byte[] cachedBody) {
this.cachedBodyInputStream = new ByteArrayInputStream(cachedBody);
}
#Override
public boolean isFinished() {
try {
return cachedBodyInputStream.available() == 0;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
#Override
public boolean isReady() {
return true;
}
#Override
public void setReadListener(ReadListener readListener) {
throw new UnsupportedOperationException();
}
#Override
public int read() throws IOException {
return cachedBodyInputStream.read();
}
}
ContentCachingFilter.java:
#Order(value = Ordered.HIGHEST_PRECEDENCE)
#Component
#WebFilter(filterName = "ContentCachingFilter", urlPatterns = "/*")
public class ContentCachingFilter extends OncePerRequestFilter {
#Override
protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException {
System.out.println("IN ContentCachingFilter ");
CachedBodyHttpServletRequest cachedBodyHttpServletRequest = new CachedBodyHttpServletRequest(httpServletRequest);
filterChain.doFilter(cachedBodyHttpServletRequest, httpServletResponse);
}
}
I also added the following dependencies to pom:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.2.0.RELEASE</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.10.0</version>
</dependency>
A tuturial and full source code is located here:
https://www.baeldung.com/spring-reading-httpservletrequest-multiple-times
If you have control over the request, you could set the content type to binary/octet-stream. This allows to query for parameters without consuming the input stream.
However, this might be specific to some application servers. I only tested tomcat, jetty seems to behave the same way according to https://stackoverflow.com/a/11434646/957103.
you can use servlet filter chain, but instead use the original one, you can create your own request yourownrequests extends HttpServletRequestWrapper.
First of all we should not read parameters within the filter. Usually the headers are read in the filter to do few authentication tasks. Having said that one can read the HttpRequest body completely in the Filter or Interceptor by using the CharStreams:
String body = com.google.common.io.CharStreams.toString(request.getReader());
This does not affect the subsequent reads at all.
I'm looking for magical Java class that will allow me to do something like this:
ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
FileOutputStream fileStream = new FileOutputStream(new File("/tmp/somefile"));
MultiOutputStream outStream = new MultiOutputStream(byteStream, fileStream);
outStream.write("Hello world".getBytes());
Basically, I want tee for OutputStreams in Java. Any ideas?
Thanks!
Try the Apache Commons TeeOutputStream.
Just roll your own. There isn't any magic at all. Using Apache's TeeOutputStream you would basically use the code below. Of course using the Apache Commons I/O library you can leverage other classes, but sometimes it is nice to actually write something for yourself. :)
public final class TeeOutputStream extends OutputStream {
private final OutputStream out;
private final OutputStream tee;
public TeeOutputStream(OutputStream out, OutputStream tee) {
if (out == null)
throw new NullPointerException();
else if (tee == null)
throw new NullPointerException();
this.out = out;
this.tee = tee;
}
#Override
public void write(int b) throws IOException {
out.write(b);
tee.write(b);
}
#Override
public void write(byte[] b) throws IOException {
out.write(b);
tee.write(b);
}
#Override
public void write(byte[] b, int off, int len) throws IOException {
out.write(b, off, len);
tee.write(b, off, len);
}
#Override
public void flush() throws IOException {
out.flush();
tee.flush();
}
#Override
public void close() throws IOException {
try {
out.close();
} finally {
tee.close();
}
}
}
Testing with the above class with the following
public static void main(String[] args) throws IOException {
TeeOutputStream out = new TeeOutputStream(System.out, System.out);
out.write("Hello world!".getBytes());
out.flush();
out.close();
}
would print Hello World!Hello World!.
(Note: the overridden close() could use some care tho' :)
Just found this thread beacause I had to face the same problem.
If someone wants to see my solution (java7 code):
package Core;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class MultiOutputStream extends OutputStream {
private List<OutputStream> out;
public MultiOutputStream(List<OutputStream> outStreams) {
this.out = new LinkedList<OutputStream>();
for (Iterator<OutputStream> i = outStreams.iterator(); i.hasNext();) {
OutputStream outputStream = (OutputStream) i.next();
if(outputStream == null){
throw new NullPointerException();
}
this.out.add(outputStream);
}
}
#Override
public void write(int arg0) throws IOException {
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(arg0);
}
}
#Override
public void write(byte[] b) throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(b);
}
}
#Override
public void write(byte[] b, int off, int len) throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.write(b, off, len);
}
}
#Override
public void close() throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.close();
}
}
#Override
public void flush() throws IOException{
for (Iterator<OutputStream> i = out.iterator(); i.hasNext();) {
OutputStream var = (OutputStream) i.next();
var.flush();
}
}
}
Works fine so far, just tested some basic operation, e.g. setting up a MultiOutputStream from the System.out Stream and 2 PrintStreams each writing into a seperate log.
I used
System.setOut(multiOutputStream);
to write to my terminal screen and two logs which worked without any problems.
final ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
final FileOutputStream fileStream = new FileOutputStream(new File("/tmp/somefile"));
OutputStream outStream = new OutputStream() {
public void write(int b) throws IOException {
byteStream.write(b);
fileStream.write(b);
}
};
outStream.write("Hello world".getBytes());
Roll your own, it's basically trivial. Use an ArrayList<OutputStream> or whatever's popular nowadays to store all the streams you want and write the write method to loop over all of them, writing to each.