I'm trying to write the output Strings into a word document using the following code :
try {
out = new PrintWriter(new BufferedWriter(new FileWriter("report.doc", true)));
out.println("<html><style>"+string1+"</style><table cellspacing = 0 cellpadding = 0><tr>" + string2 + "</html>" + (char)12);
} catch (IOException e) {
JOptionPane.showMessageDialog(null, "File error " + e.getMessage());
} finally {
if (out != null) {
try {
out.close();
} catch (Exception ignore) {
}
}
}
If this method is called (let's say) 10 times, it only writes the information of the first String. However, when I replace 'report.doc' with 'report.html', the created html file contains all the information of the 10 Strings.
How can I alter my code so that it can generate a word document with all the information as is the created html document?
You need to use a .doc processor java library. Without the help of word processor library, you need to know the format of .doc documents, just you know the structure of .html documents.
Apache poi is a good example of such a library.
Another approach is to port the MS Office libraries to a java library using COM bridges. I have been using a commercial tool for that purpose. JACOB seems an open source example of a Java-COM bridge, though I have not tested this product.
Related
I am trying to write data in java into apache parquet. So far, what i've done is use apache arrow via the examples here: https://arrow.apache.org/cookbook/java/schema.html#creating-fields and create an arrow format dataset.
Question is, how do I write it into parquet after that? Also, do I need to use apache arrow to output the data as a parquet file? or can I use apache parquet directly to serialize the data and then output it as a parquet file?
what i've done:
try (BufferAllocator allocator = new RootAllocator()) {
Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
Schema schemaPerson = new Schema(asList(name, age));
try(
VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, allocator)
){
VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
nameVector.allocateNew(3);
nameVector.set(0, "David".getBytes());
nameVector.set(1, "Gladis".getBytes());
nameVector.set(2, "Juan".getBytes());
IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
ageVector.allocateNew(3);
ageVector.set(0, 10);
ageVector.set(1, 20);
ageVector.set(2, 30);
vectorSchemaRoot.setRowCount(3);
File file = new File("randon_access_to_file.arrow");
try (
FileOutputStream fileOutputStream = new FileOutputStream(file);
ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, fileOutputStream.getChannel())
) {
writer.start();
writer.writeBatch();
writer.end();
System.out.println("Record batches written: " + writer.getRecordBlocks().size() + ". Number of rows written: " + vectorSchemaRoot.getRowCount());
} catch (IOException e) {
e.printStackTrace();
}
}
}
but this outputs as an arrow file. not a parquet. Any ideas how I can output this to parquet file instead? And do i need arrow to generate a parquet file to begin with - or can i just use parquet directly?
Arrow Java does not yet support writing to Parquet files, but you can use Parquet to do that.
There is some code in the Arrow dataset test classes that may help. See
org.apache.arrow.dataset.ParquetWriteSupport;
org.apache.arrow.dataset.file.TestFileSystemDataset;
The second class has some tests that use the utilities in the first one.
You can find them on GitHub here:
https://github.com/apache/arrow/tree/master/java/dataset/src/test/java/org/apache/arrow/dataset
I am coding with Java and I am trying to write in some forex data into a CSV file. I want the CSV file to be constantly the latest 277 datas without stacking on top of old data. So I used the "new FileWriter(file, false).close();" to empty the former data every time before the program writes in data. The code works as the newest Data starts always from index 1 in CSV opened with excel and the rest are blank. But the csv file size keeps increasing. Could anyone give me any ideas on how to modify the code so that the file size would not increase indefinitely?
//this is the inside of a loop that starts every time a candle stick gets formed
try {
new FileWriter(file, false).close();
} catch (Exception e) {
console.getErr().println(e.getMessage());
e.printStackTrace(console.getErr());
context.stop();
}
int shift = 1;
while (shift < 278){
IBar bar = history.getBar(Instrument.USDJPY, Period.FIVE_MINS, OfferSide.BID, shift);
try {
out.write(dateFormat.format(bar.getTime()) + "," + priceFormat.format(bar.getOpen()) + "," + priceFormat.format(bar.getHigh()) + ","
+ priceFormat.format(bar.getLow()) + "," + priceFormat.format(bar.getClose()) + "," + priceFormat.format(askBar.getVolume()) + "\r\n");
} catch (Exception e) {
console.getErr().println(e.getMessage());
e.printStackTrace(console.getErr());
context.stop();
}
shift+=1;
}//while
try {
out.flush();
} catch (Exception e) {
console.getErr().println(e.getMessage());
e.printStackTrace(console.getErr());
context.stop();
}
Edit: I opened the CSV with notepad and saw an egregious amount of space and had to scroll far down to see the data. When I open properties of the CSV files, the size says 253 KB but the "size on disk" is 3.87 mb, which I don't understand. Anyway to solve this?
Edit2: Stopping the program on the Fx platform app from running presumably closed the Bufferwriter named "out" and the "size on disk" returns to normal. But still no idea on the space problem. Also somehow I can't manually edit it with notepad, it says I have no access to change the file when I attempt to save. I am new to programming so I don't know what did that either. Thank you.
Edit3: Solved it. The out.flush was the culprit, replaced it with out.close, and create a new bufferwriter named "out" every time this class gets started.
I have this application I'm developing in JSP and I wish to export some data from the database in XLS (MS Excel format).
Is it possible under tomcat to just write a file as if it was a normal Java application, and then generate a link to this file? Or do I need to use a specific API for it?
Will I have permission problems when doing this?
While you can use a full fledged library like JExcelAPI, Excel will also read CSV and plain HTML tables provided you set the response MIME Type to something like "application/vnd.ms-excel".
Depending on how complex the spreadsheet needs to be, CSV or HTML can do the job for you without a 3rd party library.
Don't use plain HTML tables with an application/vnd.ms-excel content type. You're then basically fooling Excel with a wrong content type which would cause failure and/or warnings in the latest Excel versions. It will also messup the original HTML source when you edit and save it in Excel. Just don't do that.
CSV in turn is a standard format which enjoys default support from Excel without any problems and is in fact easy and memory-efficient to generate. Although there are libraries out, you can in fact also easily write one in less than 20 lines (funny for ones who can't resist). You just have to adhere the RFC 4180 spec which basically contains only 3 rules:
Fields are separated by a comma.
If a comma occurs within a field, then the field has to be surrounded by double quotes.
If a double quote occurs within a field, then the field has to be surrounded by double quotes and the double quote within the field has to be escaped by another double quote.
Here's a kickoff example:
public static <T> void writeCsv (List<List<T>> csv, char separator, OutputStream output) throws IOException {
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(output, "UTF-8"));
for (List<T> row : csv) {
for (Iterator<T> iter = row.iterator(); iter.hasNext();) {
String field = String.valueOf(iter.next()).replace("\"", "\"\"");
if (field.indexOf(separator) > -1 || field.indexOf('"') > -1) {
field = '"' + field + '"';
}
writer.append(field);
if (iter.hasNext()) {
writer.append(separator);
}
}
writer.newLine();
}
writer.flush();
}
Here's an example how you could use it:
public static void main(String[] args) throws IOException {
List<List<String>> csv = new ArrayList<List<String>>();
csv.add(Arrays.asList("field1", "field2", "field3"));
csv.add(Arrays.asList("field1,", "field2", "fie\"ld3"));
csv.add(Arrays.asList("\"field1\"", ",field2,", ",\",\",\""));
writeCsv(csv, ',', System.out);
}
And inside a Servlet (yes, Servlet, don't use JSP for this!) you can basically do:
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getPathInfo().substring(1);
List<List<Object>> csv = someDAO().findCsvContentFor(filename);
response.setHeader("content-type", "text/csv");
response.setHeader("content-disposition", "attachment;filename=\"" + filename + "\"");
writeCsv(csv, ';', response.getOutputStream());
}
Map this servlet on something like /csv/* and invoke it as something like http://example.com/context/csv/filename.csv. That's all.
Note that I added the possiblity to specify the separator character separately, because it may depend on the locale used whether Excel would accept a comma , or semicolon ; as CSV field separator. Note that I also added the filename to the URL pathinfo, because a certain webbrowser developed by a team in Redmond otherwise wouldn't save the download with the proper filename.
You will probably need a library to manipulate Excel files, like JExcelAPI ("jxl") or POI. I'm more familiar with jxl and it can certainly write files. You can generate them and store them by serving a URL to them but I wouldn't. Generated files are a pain. They add complication in the form on concurrency, clean-up processes, etc.
If you can generate the file on the fly and stream it to the client through the standard servlet mechanisms.
If it's generated many, may times or the generation is expensive then you can cache the result somehow but I'd be more inclined to keep it in memory than as a file. I'd certainly avoid, if you can, linking directly to the generated file by URL. If you go via a servlet it'll allow you to change your impleemntation later. It's the same encapsualtion concept as in OO dsign.
POI or JExcel are good APIs. I personally like better POI, plus POI is constantly updated. Furthermore, there are more resources online about POI than JExcel in case you have any questions. However, either of the two does a great job.
maybe you should consider using some reporting tool with an option of exporting files into XLS format. my suggestion is JasperReports
try {
String absoluteDiskPath = test.xls";
File f = new File(absoluteDiskPath);
response.setContentType("application/xlsx");
response.setHeader("Content-Disposition", "attachment; filename=" + absoluteDiskPath);
String name = f.getName().substring(f.getName().lastIndexOf("/") + 1, f.getName().length());
InputStream in = new FileInputStream(f);
out.clear(); //clear outputStream prevent illegalStateException write binary data to outputStream
ServletOutputStream outs = response.getOutputStream();
int bit = 256;
int i = 0;
try {
while ((bit) >= 0) {
bit = in.read();
outs.write(bit);
}
outs.flush();
outs.close();
in.close();
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
try {
if(outs != null)
outs.close();
if(in != null)
in.close();
}catch (Exception ioe2) {
ioe2.printStackTrace();
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
I tried like as below in JSP, it is working fine.
<% String filename = "xyz.xls";
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition","attachment; filename=\"" + filename + "\"");
java.io.File excelFile=new java.io.File("C:\\Users\\hello\\Desktop\\xyz.xls");
java.io.FileInputStream fileInputStream=new java.io.FileInputStream(excelFile);
byte[] bytes = new byte[(int) excelFile.length()];
int offset = 0;
while (offset < bytes.length)
{
int result = fileInputStream.read(bytes, offset, bytes.length - offset);
if (result == -1) {
break;
}
offset += result;
}
javax.servlet.ServletOutputStream outs = response.getOutputStream();
outs.write(bytes);
outs.flush();
outs.close();
fileInputStream.close();
%>
I have no idea how can I insert boolean sign into RTF document from java programm. I think about √ or ✓ and –. I tried insert these signs to clear document and save it as *.rtf and then open it in Notepad++ but there is a lot of codes (~160 lines) and I can not understand what is it. Do you have any idea?
After a short search I found this:
Writing unicode to rtf file
So a final code version would be:
public void writeToFile() {
String strJapanese = "日本語✓";
try {
FileOutputStream fos = new FileOutputStream("test.rtf");
Writer out = new OutputStreamWriter(fos, "UTF8");
out.write(strJapanese);
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Please read about RTF
√ or ✓ and – are not available in every charset, so specify it. If yout output in UTF-8 (and i advise you to do so, check here on how to do this). You might need to encode the sign aswell, check Wikipedia
I have this application I'm developing in JSP and I wish to export some data from the database in XLS (MS Excel format).
Is it possible under tomcat to just write a file as if it was a normal Java application, and then generate a link to this file? Or do I need to use a specific API for it?
Will I have permission problems when doing this?
While you can use a full fledged library like JExcelAPI, Excel will also read CSV and plain HTML tables provided you set the response MIME Type to something like "application/vnd.ms-excel".
Depending on how complex the spreadsheet needs to be, CSV or HTML can do the job for you without a 3rd party library.
Don't use plain HTML tables with an application/vnd.ms-excel content type. You're then basically fooling Excel with a wrong content type which would cause failure and/or warnings in the latest Excel versions. It will also messup the original HTML source when you edit and save it in Excel. Just don't do that.
CSV in turn is a standard format which enjoys default support from Excel without any problems and is in fact easy and memory-efficient to generate. Although there are libraries out, you can in fact also easily write one in less than 20 lines (funny for ones who can't resist). You just have to adhere the RFC 4180 spec which basically contains only 3 rules:
Fields are separated by a comma.
If a comma occurs within a field, then the field has to be surrounded by double quotes.
If a double quote occurs within a field, then the field has to be surrounded by double quotes and the double quote within the field has to be escaped by another double quote.
Here's a kickoff example:
public static <T> void writeCsv (List<List<T>> csv, char separator, OutputStream output) throws IOException {
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(output, "UTF-8"));
for (List<T> row : csv) {
for (Iterator<T> iter = row.iterator(); iter.hasNext();) {
String field = String.valueOf(iter.next()).replace("\"", "\"\"");
if (field.indexOf(separator) > -1 || field.indexOf('"') > -1) {
field = '"' + field + '"';
}
writer.append(field);
if (iter.hasNext()) {
writer.append(separator);
}
}
writer.newLine();
}
writer.flush();
}
Here's an example how you could use it:
public static void main(String[] args) throws IOException {
List<List<String>> csv = new ArrayList<List<String>>();
csv.add(Arrays.asList("field1", "field2", "field3"));
csv.add(Arrays.asList("field1,", "field2", "fie\"ld3"));
csv.add(Arrays.asList("\"field1\"", ",field2,", ",\",\",\""));
writeCsv(csv, ',', System.out);
}
And inside a Servlet (yes, Servlet, don't use JSP for this!) you can basically do:
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getPathInfo().substring(1);
List<List<Object>> csv = someDAO().findCsvContentFor(filename);
response.setHeader("content-type", "text/csv");
response.setHeader("content-disposition", "attachment;filename=\"" + filename + "\"");
writeCsv(csv, ';', response.getOutputStream());
}
Map this servlet on something like /csv/* and invoke it as something like http://example.com/context/csv/filename.csv. That's all.
Note that I added the possiblity to specify the separator character separately, because it may depend on the locale used whether Excel would accept a comma , or semicolon ; as CSV field separator. Note that I also added the filename to the URL pathinfo, because a certain webbrowser developed by a team in Redmond otherwise wouldn't save the download with the proper filename.
You will probably need a library to manipulate Excel files, like JExcelAPI ("jxl") or POI. I'm more familiar with jxl and it can certainly write files. You can generate them and store them by serving a URL to them but I wouldn't. Generated files are a pain. They add complication in the form on concurrency, clean-up processes, etc.
If you can generate the file on the fly and stream it to the client through the standard servlet mechanisms.
If it's generated many, may times or the generation is expensive then you can cache the result somehow but I'd be more inclined to keep it in memory than as a file. I'd certainly avoid, if you can, linking directly to the generated file by URL. If you go via a servlet it'll allow you to change your impleemntation later. It's the same encapsualtion concept as in OO dsign.
POI or JExcel are good APIs. I personally like better POI, plus POI is constantly updated. Furthermore, there are more resources online about POI than JExcel in case you have any questions. However, either of the two does a great job.
maybe you should consider using some reporting tool with an option of exporting files into XLS format. my suggestion is JasperReports
try {
String absoluteDiskPath = test.xls";
File f = new File(absoluteDiskPath);
response.setContentType("application/xlsx");
response.setHeader("Content-Disposition", "attachment; filename=" + absoluteDiskPath);
String name = f.getName().substring(f.getName().lastIndexOf("/") + 1, f.getName().length());
InputStream in = new FileInputStream(f);
out.clear(); //clear outputStream prevent illegalStateException write binary data to outputStream
ServletOutputStream outs = response.getOutputStream();
int bit = 256;
int i = 0;
try {
while ((bit) >= 0) {
bit = in.read();
outs.write(bit);
}
outs.flush();
outs.close();
in.close();
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
try {
if(outs != null)
outs.close();
if(in != null)
in.close();
}catch (Exception ioe2) {
ioe2.printStackTrace();
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
I tried like as below in JSP, it is working fine.
<% String filename = "xyz.xls";
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition","attachment; filename=\"" + filename + "\"");
java.io.File excelFile=new java.io.File("C:\\Users\\hello\\Desktop\\xyz.xls");
java.io.FileInputStream fileInputStream=new java.io.FileInputStream(excelFile);
byte[] bytes = new byte[(int) excelFile.length()];
int offset = 0;
while (offset < bytes.length)
{
int result = fileInputStream.read(bytes, offset, bytes.length - offset);
if (result == -1) {
break;
}
offset += result;
}
javax.servlet.ServletOutputStream outs = response.getOutputStream();
outs.write(bytes);
outs.flush();
outs.close();
fileInputStream.close();
%>