Using com.sun.codemodel; how to write class as String instead of to a File

Question

I am investigating com.sun.codemodel to generate Java classes.

// https://mvnrepository.com/artifact/com.sun.codemodel/codemodel
compile group: 'com.sun.codemodel', name: 'codemodel', version: '2.6'

The JCodeModel class has multiple build methods that support generating the required Java classes to files, however I would like to obtain theses generated classes as Strings.

Looking at the Javadoc and source code of JCodeModel I cannot see anyway to achieve this.

How can I obtain my generated classes as a String instead of/as well as having them written to a file?

Is it possible to extend com.sun.codemodel.CodeWriter to produce a String?

Answer 1

Sure! Producing just a String is a little tricky though since JCodeModel produces multiple classes. You can look up those classes and output them as Strings using a custom CodeWriter as follows:

JCodeModel codeModel = new JCodeModel();

JDefinedClass testClass = codeModel._class("test.Test");
testClass.method(JMod.PUBLIC, codeModel.VOID, "helloWorld");

final Map<String, ByteArrayOutputStream> streams = new HashMap<String, ByteArrayOutputStream>();

CodeWriter codeWriter = new CodeWriter() {
    @Override
    public OutputStream openBinary(JPackage jPackage, String name) {
        String fullyQualifiedName = jPackage.name().length() == 0 ? name : jPackage.name().replace(".", "/") + "/" + name;

        if(!streams.containsKey(fullyQualifiedName)) {
            streams.put(fullyQualifiedName, new ByteArrayOutputStream());
        }
        return streams.get(fullyQualifiedName);
    }

    @Override
    public void close() throws IOException {
        for (OutputStream outputStream : streams.values()) {
            outputStream.flush();
            outputStream.close();
        }
    }
};

codeModel.build(codeWriter);

System.out.println(streams.get("test/Test.java"));

Outputs:

public class Test {


    public void helloWorld() {
    }

}