[java] Get an OutputStream into a String

What's the best way to pipe the output from an java.io.OutputStream to a String in Java?

Say I have the method:

  writeToStream(Object o, OutputStream out)

Which writes certain data from the object to the given stream. However, I want to get this output into a String as easily as possible.

I'm considering writing a class like this (untested):

class StringOutputStream extends OutputStream {

  StringBuilder mBuf;

  public void write(int byte) throws IOException {
    mBuf.append((char) byte);
  }

  public String getString() {
    return mBuf.toString();
  }
}

But is there a better way? I only want to run a test!

This worked nicely

OutputStream output = new OutputStream() {
    private StringBuilder string = new StringBuilder();

    @Override
    public void write(int b) throws IOException {
        this.string.append((char) b );
    }

    //Netbeans IDE automatically overrides this toString()
    public String toString() {
        return this.string.toString();
    }
};

method call =>> marshaller.marshal( (Object) toWrite , (OutputStream) output);

then to print the string or get it just reference the "output" stream itself As an example, to print the string out to console =>> System.out.println(output);

FYI: my method call marshaller.marshal(Object,Outputstream) is for working with XML. It is irrelevant to this topic.

This is highly wasteful for productional use, there is a way too many conversion and it is a bit loose. This was just coded to prove to you that it is totally possible to create a custom OuputStream and output a string. But just go Horcrux7 way and all is good with merely two method calls.

And the world lives on another day....

Here's what I ended up doing:

Obj.writeToStream(toWrite, os);
try {
    String out = new String(os.toByteArray(), "UTF-8");
    assertTrue(out.contains("testString"));
} catch (UnsupportedEncondingException e) {
    fail("Caught exception: " + e.getMessage());
}

Where os is a ByteArrayOutputStream.

baos.toString(StandardCharsets.UTF_8);

Converts the buffer's contents into a string by decoding the bytes using the named charset.

Java 14 - https://docs.oracle.com/

I like the Apache Commons IO library. Take a look at its version of ByteArrayOutputStream, which has a toString(String enc) method as well as toByteArray(). Using existing and trusted components like the Commons project lets your code be smaller and easier to extend and repurpose.

Here's what I ended up doing:

Obj.writeToStream(toWrite, os);
try {
    String out = new String(os.toByteArray(), "UTF-8");
    assertTrue(out.contains("testString"));
} catch (UnsupportedEncondingException e) {
    fail("Caught exception: " + e.getMessage());
}

Where os is a ByteArrayOutputStream.

baos.toString(StandardCharsets.UTF_8);

Converts the buffer's contents into a string by decoding the bytes using the named charset.

Java 14 - https://docs.oracle.com/

I like the Apache Commons IO library. Take a look at its version of ByteArrayOutputStream, which has a toString(String enc) method as well as toByteArray(). Using existing and trusted components like the Commons project lets your code be smaller and easier to extend and repurpose.

This worked nicely

OutputStream output = new OutputStream() {
    private StringBuilder string = new StringBuilder();

    @Override
    public void write(int b) throws IOException {
        this.string.append((char) b );
    }

    //Netbeans IDE automatically overrides this toString()
    public String toString() {
        return this.string.toString();
    }
};

method call =>> marshaller.marshal( (Object) toWrite , (OutputStream) output);

then to print the string or get it just reference the "output" stream itself As an example, to print the string out to console =>> System.out.println(output);

FYI: my method call marshaller.marshal(Object,Outputstream) is for working with XML. It is irrelevant to this topic.

This is highly wasteful for productional use, there is a way too many conversion and it is a bit loose. This was just coded to prove to you that it is totally possible to create a custom OuputStream and output a string. But just go Horcrux7 way and all is good with merely two method calls.

And the world lives on another day....

Here's what I ended up doing:

Obj.writeToStream(toWrite, os);
try {
    String out = new String(os.toByteArray(), "UTF-8");
    assertTrue(out.contains("testString"));
} catch (UnsupportedEncondingException e) {
    fail("Caught exception: " + e.getMessage());
}

Where os is a ByteArrayOutputStream.

I like the Apache Commons IO library. Take a look at its version of ByteArrayOutputStream, which has a toString(String enc) method as well as toByteArray(). Using existing and trusted components like the Commons project lets your code be smaller and easier to extend and repurpose.