How compile Groovy source but not from filesystem

问题:

I compile single groovy source module "in fly" using GroovyClassLoader.parseClass(src) and all is ok.

But problem is when this source module imports other classes, these are not compiled yet. Traditional compiling when I start compilation of one source but other are required and ready on source path, are compiled too.

How can I use GroovyClassLoader with target to compile all other required sources NOT FROM FILESYSYSTEM. My sources are for example in database, remote http via URI etc.

回答1:

The key is to make custom URL handling -- you have to implement a URLStreamHandler and a URLConnection.

If you google around, there's some good documentation on how to implement the stream handler and connection classes -- but for what you're doing, you really only need dummy implementations.

Here's some source code to bootstrap you -- it demonstrates how to connect the pieces up. If you provide some implementation of lookupScriptCodeWithJDBCorWhatever you'll be good to go.

import groovy.lang.GroovyResourceLoader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;

public class CustomGroovyResourceLoader implements GroovyResourceLoader {

    private final GroovyResourceLoader parentLoader;

    public CustomGroovyResourceLoader(GroovyResourceLoader parentLoader) {
        this.parentLoader = parentLoader;
    }

    @Override
    public URL loadGroovySource(String filename) throws MalformedURLException {
        URL resourceURL = null;

        if (parentLoader != null) {
            resourceURL = parentLoader.loadGroovySource(filename);
        }

        if (resourceURL == null) {
            resourceURL = createURL(filename);
        }

        return resourceURL;
    }

    public URL createURL(String resourceName) throws MalformedURLException {

        String scriptSourceCode = lookupScriptCodeWithJDBCorWhatever(resourceName);

        return new URL(null, "groovy:///" + resourceName,
                new GroovyResourceStreamHandler(scriptSourceCode));

    }

    private String lookupScriptCodeWithJDBCorWhatever(String resourceName) {

        //TODO: blah blah blah
        return null;
    }

    class GroovyResourceConnection extends URLConnection {

        private final String urlData;

        protected GroovyResourceConnection(URL url, String logic) {
            super(url);
            this.urlData = logic;
        }

        @Override
        public void connect() throws IOException {}

        @Override
        public InputStream getInputStream() throws IOException {
            return new ByteArrayInputStream(urlData.getBytes());
        }
    }

    class GroovyResourceStreamHandler extends URLStreamHandler {

        private final String scriptSource;

        public GroovyResourceStreamHandler(String scriptSource) {
            this.scriptSource = scriptSource;
        }

        @Override
        protected URLConnection openConnection(URL u) throws IOException {
            GroovyResourceConnection connection = new GroovyResourceConnection(u, scriptSource);
            return connection;

        }
    }

}

You then install this thing with some code that looks like this:

GroovyClassLoader groovyClassLoader = new GroovyClassLoader();
groovyClassLoader.setResourceLoader( new CustomGroovyResourceLoader( groovyClassLoader.getResourceLoader() ) );