I want to write a class object to the string and then again create an object from it.
I searched on the net but all I found is to write an object to file however I want to write in the string, not on file.
Below is the example of writing to file similarly I want to write in String or similar Object and not in the file.
some_class implements serializable {
...
}
FileOutputStream f = new FileOutputStream(new File("myObjects.txt"));
ObjectOutputStream o = new ObjectOutputStream(f);
// Write objects to file
o.writeObject(object1);
o.close();
f.close();
FileInputStream fi = new FileInputStream(new File("myObjects.txt"));
ObjectInputStream oi = new ObjectInputStream(fi);
// Read objects
some_class object2 = (some_class) oi.readObject();
oi.close();
fi.close();
Please help with the same.
This would be one way:
try
{
// To String
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream os = new ObjectOutputStream(bos);
os.writeObject(object1);
String serializedObject1 = bos.toString();
os.close();
// To Object
ByteArrayInputStream bis = new ByteArrayInputStream(serializedObject1.getBytes());
ObjectInputStream oInputStream = new ObjectInputStream(bis);
YourObject restoredObject1 = (YourObject) oInputStream.readObject();
oInputStream.close();
} catch(Exception ex) {
ex.printStackTrace();
}
I would prefer the Base64 way though.
This would be an example of encoding:
private static String serializableToString( Serializable o ) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(o);
oos.close();
return Base64.getEncoder().encodeToString(baos.toByteArray());
}
And this is an example of decoding:
private static Object objectFromString(String s) throws IOException, ClassNotFoundException
{
byte [] data = Base64.getDecoder().decode(s);
ObjectInputStream ois = new ObjectInputStream(
new ByteArrayInputStream(data));
Object o = ois.readObject();
ois.close();
return o;
}
the best way to serialize an object to String and vice versa you should convert the object into JSON String and encode into base64. and to get object decode base64 and convert to object using GSON (opensource google provide java library)
class foo{ String name, email;
//setter getter
}
convert Object to base64 JSON
public static String convertToJson(Object o){
String result=new Gson().toJson(o);
return Base64.getEncoder().encodeToString(result);
}
//read base64
public static <T> T convertJsonToObject(String base64Object,Class<T> classOfT){
Gson gson = new Gson();
return gson.fromJson(new InputStreamReader(new ByteArrayInputStream(Base64.getDecoder().decode(base64Object))),classOfT);
}
public static void main(String[] args) {
foo obj=new foo("jhon","jhon#gamil.com");
String json=convertToJson(foo);
System.out.println(json);
foo obj_fromJson=convertJsonToObject(json,foo.class);
System.out.println(obj_fromJson.getName());
}
Related
Alright so I've got this Android Studio app with user class
public class User{
int age;
String name;
int yearOfBirth;
}
And then I've got this two methods
public static Object fromString(String s) throws IOException,ClassNotFoundException {
byte [] data = Base64.getDecoder().decode(s);
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(data));
Object o = ois.readObject();
ois.close();
return o;
}
public static String toString(Serializable o) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(o);
oos.close();
return Base64.getEncoder().encodeToString(baos.toByteArray());
}
So I create User object, convert it to String, save it to database on other device where I need to convert the object back to User object to change some stuff, convert to String again save to database and then be able to decode the User object in my app again.
Problem is when trying to decode the String on the server side I'm getting this exception
Exception in thread "main" java.lang.ClassNotFoundException: com.example.mikithenics.User
What could be the possible solution ? Any help is appreciated.
You can serialize this using Google Gson lib like this:
Gson gson = new Gson();
String jsonString = gson.toJson(userObject);
And deserialize like this:
Gson gson = new Gson();
User userObject = gson.fromJson(userJsonString, User.class);
To use Gson lib, put this in your app build.gradle file, inside dependencies:
implementation 'com.google.code.gson:gson:2.8.6'
How to compress a Java pojo object using Gzip?
Below code compress a string -
public static String compress(String str, String inEncoding) {
if (str == null || str.length() == 0) {
return str;
}
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(out);
gzip.write(str.getBytes(inEncoding));
gzip.close();
return URLEncoder.encode(out.toString("ISO-8859-1"), "UTF-8");
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
Instead of String str as a parameter, how to use below pojo class object (Client cc) and compress?
Pojo class -
Class client {
Public string name;
Public string location;
//Getter and setter methods
}
How can i compress and decompress this client pojo class using gzip.?
You can compress your Client class which implements serializable using gzip by doing the following :
public static bytes[] compressThis(Client client){
ByteArrayOutputStream baos = new ByteArrayOutputStream();
GZIPOutputStream gzipOut = new GZIPOutputStream(client);
ObjectOutputStream objectOut = new ObjectOutputStream(gzipOut);
objectOut.writeObject(client);
objectOut.close();
return baos.toByteArray();
}
Following which you can decompress it by doing the following :
public static getClientFrom(bytes[] bytes){
ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
GZIPInputStream gzipIn = new GZIPInputStream(bais);
ObjectInputStream objectIn = new ObjectInputStream(gzipIn);
Client client = (Client) objectIn.readObject();
objectIn.close();
return client;
}
I want to object AuditContainer convert to byte and then save in file:
public class AuditContainer implements Serializable {
private Paint mPaint;
private Path mPath;
private int x,y;
private String text;
boolean is_text;
Problem is because Paint and Path must be serialized, but it cant..
Firstly i want make serialization for this class, but i have got one truble, i cant save all things which i need.
My question is how i can convert AuditoContainer to byte? Is it Posible? and which is princips/options for save my class in file/database?
I need help, please.
If what you want is to write the status of the object to a file, is better if you don't use serialization. Serialization has lots of flaws and is hard to get it done correctly, while you can save the properties of your object easily as strings in the file.
want serialization example ?
ok here is one (make sure that all your Objects mentioned in your variables are serializable as well)
public void save(AuditContainer auditContainer, File file) throws FileNotFoundException, IOException {
FileOutputStream fos = null;
ObjectOutputStream oos = null;
try{
fos = new FileOutputStream(file);
oos = new ObjectOutputStream(fos);
oos.writeObject(auditContainer);
}finally{
if(oos != null){
oos.flush();
oos.close();
}
}
}
public AuditContainer load(File file) throws FileNotFoundException, IOException, ClassNotFoundException {
AuditContainer auditContainer = null;
FileInputStream fis = null;
ObjectInputStream ois = null;
try{
fis = new FileInputStream(file);
ois = new ObjectInputStream(ois);
auditContainer = (AuditContainer)ois.readObject();
}finally{
if(ois != null){
ois.close();
}
}
return auditContainer;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(reg_be);
oos.flush();
oos.close();
InputStream is = new ByteArrayInputStream(baos.toByteArray());
This code convert Java Object to InputStream and how can I convert InputStream to an Object? I need to convert my Object to an InputStream then I pass it and I want to get my Object back.
In try block you should write:
ObjectInputStream ois = new ObjectInputStream(is);
Object object = ois.readObject();
ObjectInputStream is initialized with another stream, e.g. BufferedInputStream or your input stream is.
ObjectInputStream ois = new ObjectInputStream(is);
Object object = ois.readObject();
Try the following
ObjectInputStream ois = new ObjectInputStream(is);
Object obj = ois .readObject();
ObjectInputStream ois = new ObjectInputStream(is);
Object object = ois.readObject();
As mentioned by #darijan is working fine.
But again we need to do try, catch block for that code, & for blank input stream it will give EOF (End Of File) related error.
So, I am converting it to a string. Then if the string is not empty or null, then only I am converting it to Object using ObjectMapper
Although it's not an efficient approach, I don't need to worry about try-catch, null handling also is done in a string instead of the input stream
String responseStr = IOUtils.toString(is, StandardCharsets.UTF_8.name());
Object object = null;
// is not null or whitespace consisted string
if (StringUtils.isNotBlank(response)) {
object = getJsonFromString(response);
}
// below codes are already used in project (Util classes)
private Object getJsonFromString(String jsonStr) {
if (StringUtils.isEmpty(jsonStr)) {
return new LinkedHashMap<>();
}
ObjectMapper objectMapper = getObjectMapper();
Map<Object, Object> obj = null;
try {
obj = objectMapper.readValue(jsonStr, new TypeReference<Map<Object, Object>>() {
});
} catch (IOException e) {
LOGGER.error("Unable to parse JSON : {}",e)
}
return obj;
}
private ObjectMapper getObjectMapper() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
objectMapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
return objectMapper;
}
Let's say I have a serializable class AppMessage.
I would like to transmit it as byte[] over sockets to another machine where it is rebuilt from the bytes received.
How could I achieve this?
Prepare the byte array to send:
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = null;
try {
out = new ObjectOutputStream(bos);
out.writeObject(yourObject);
out.flush();
byte[] yourBytes = bos.toByteArray();
...
} finally {
try {
bos.close();
} catch (IOException ex) {
// ignore close exception
}
}
Create an object from a byte array:
ByteArrayInputStream bis = new ByteArrayInputStream(yourBytes);
ObjectInput in = null;
try {
in = new ObjectInputStream(bis);
Object o = in.readObject();
...
} finally {
try {
if (in != null) {
in.close();
}
} catch (IOException ex) {
// ignore close exception
}
}
The best way to do it is to use SerializationUtils from Apache Commons Lang.
To serialize:
byte[] data = SerializationUtils.serialize(yourObject);
To deserialize:
YourObject yourObject = SerializationUtils.deserialize(data)
As mentioned, this requires Commons Lang library. It can be imported using Gradle:
compile 'org.apache.commons:commons-lang3:3.5'
Maven:
<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
Jar file
And more ways mentioned here
Alternatively, the whole collection can be imported. Refer this link
If you use Java >= 7, you could improve the accepted solution using try with resources:
private byte[] convertToBytes(Object object) throws IOException {
try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(bos)) {
out.writeObject(object);
return bos.toByteArray();
}
}
And the other way around:
private Object convertFromBytes(byte[] bytes) throws IOException, ClassNotFoundException {
try (ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
ObjectInputStream in = new ObjectInputStream(bis)) {
return in.readObject();
}
}
Can be done by SerializationUtils, by serialize & deserialize method by ApacheUtils to convert object to byte[] and vice-versa , as stated in #uris answer.
To convert an object to byte[] by serializing:
byte[] data = SerializationUtils.serialize(object);
To convert byte[] to object by deserializing::
Object object = (Object) SerializationUtils.deserialize(byte[] data)
Click on the link to Download org-apache-commons-lang.jar
Integrate .jar file by clicking:
FileName -> Open Medule Settings -> Select your module -> Dependencies -> Add Jar file and you are done.
Hope this helps.
I also recommend to use SerializationUtils tool. I want to make a ajust on a wrong comment by #Abilash. The SerializationUtils.serialize() method is not restricted to 1024 bytes, contrary to another answer here.
public static byte[] serialize(Object object) {
if (object == null) {
return null;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
try {
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(object);
oos.flush();
}
catch (IOException ex) {
throw new IllegalArgumentException("Failed to serialize object of type: " + object.getClass(), ex);
}
return baos.toByteArray();
}
At first sight， you may think that new ByteArrayOutputStream(1024) will only allow a fixed size. But if you take a close look at the ByteArrayOutputStream, you will figure out the the stream will grow if necessary:
This class implements an output stream in which the data is
written into a byte array. The buffer automatically grows as data
is written to it.
The data can be retrieved using toByteArray() and
toString().
Another interesting method is from com.fasterxml.jackson.databind.ObjectMapper
byte[] data = new ObjectMapper().writeValueAsBytes(JAVA_OBJECT_HERE)
Maven Dependency
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
If you are using spring, there's a util class available in spring-core. You can simply do
import org.springframework.util.SerializationUtils;
byte[] bytes = SerializationUtils.serialize(anyObject);
Object object = SerializationUtils.deserialize(bytes);
I would like to transmit it as byte[] over sockets to another machine
// When you connect
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
// When you want to send it
oos.writeObject(appMessage);
where it is rebuilt from the bytes received.
// When you connect
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
// When you want to receive it
AppMessage appMessage = (AppMessage)ois.readObject();
Spring Framework org.springframework.util.SerializationUtils
byte[] data = SerializationUtils.serialize(obj);
In case you want a nice no dependencies copy-paste solution. Grab the code below.
Example
MyObject myObject = ...
byte[] bytes = SerializeUtils.serialize(myObject);
myObject = SerializeUtils.deserialize(bytes);
Source
import java.io.*;
public class SerializeUtils {
public static byte[] serialize(Serializable value) throws IOException {
ByteArrayOutputStream out = new ByteArrayOutputStream();
try(ObjectOutputStream outputStream = new ObjectOutputStream(out)) {
outputStream.writeObject(value);
}
return out.toByteArray();
}
public static <T extends Serializable> T deserialize(byte[] data) throws IOException, ClassNotFoundException {
try(ByteArrayInputStream bis = new ByteArrayInputStream(data)) {
//noinspection unchecked
return (T) new ObjectInputStream(bis).readObject();
}
}
}
This is just an optimized code form of the accepted answer in case anyone wants to use this in production :
public static void byteArrayOps() throws IOException, ClassNotFoundException{
String str="123";
byte[] yourBytes = null;
// Convert to byte[]
try(ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(bos);) {
out.writeObject(str);
out.flush();
yourBytes = bos.toByteArray();
} finally {
}
// convert back to Object
try(ByteArrayInputStream bis = new ByteArrayInputStream(yourBytes);
ObjectInput in = new ObjectInputStream(bis);) {
Object o = in.readObject();
} finally {
}
}
code example with java 8+:
public class Person implements Serializable {
private String lastName;
private String firstName;
public Person() {
}
public Person(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
#Override
public String toString() {
return "firstName: " + firstName + ", lastName: " + lastName;
}
}
public interface PersonMarshaller {
default Person fromStream(InputStream inputStream) {
try (ObjectInputStream objectInputStream = new ObjectInputStream(inputStream)) {
Person person= (Person) objectInputStream.readObject();
return person;
} catch (IOException | ClassNotFoundException e) {
System.err.println(e.getMessage());
return null;
}
}
default OutputStream toStream(Person person) {
try (OutputStream outputStream = new ByteArrayOutputStream()) {
ObjectOutput objectOutput = new ObjectOutputStream(outputStream);
objectOutput.writeObject(person);
objectOutput.flush();
return outputStream;
} catch (IOException e) {
System.err.println(e.getMessage());
return null;
}
}
}