Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.programmer > #7357

Re: Using sun javac to parse java source

Show all headers | View raw

On 8/24/2011 4:51 AM, Sebastian wrote:
> Am 24.08.2011 01:00, schrieb Arne Vajhøj:
>> On 8/23/2011 4:24 PM, Alex J wrote:
>>> I'm curious whether it is possible to use JavacParser -
>>> http://docjar.org/docs/api/com/sun/tools/javac/parser/JavacParser.html
>>> - built-in to OpenJDK to parse standalone java files (though claimed
>>> to be "internal use only API"). I googled but I've found no answers.
>>
>> Java 1.6 and newer contains a supported callable Java compiler.
>>
>> Use that.
>>
>> If you only want to syntax check you will need to discard the
>> generated byte code in case of success, but that is easy.
>>
>> The API is a bit complex many would say over engineered, but
>> it works fine.

> You might find a detailed example useful. There is an article
> about "Dynamic Code Generation with Java Compiler API in Java 6"
> by Swaminathan Bhaskar at
>
> http://www.scribd.com/doc/56642760/Java-Compiler
>
> The article shows how to compile source from strings to byte arrays.

I have a slightly differentexample - see below.

Arne

====

package test;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.URI;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.FileObject;
import javax.tools.ForwardingJavaFileManager;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import javax.tools.JavaCompiler.CompilationTask;

public class JC {
     public static void dynamicCall(String clznam, String src, String 
cp, String metnam) throws Exception {
         SpecialClassLoader xcl = new SpecialClassLoader();
         compileMemoryMemory(src, cp, clznam, xcl, System.err);
         Class<?> c = Class.forName(clznam, true, xcl);
         Object o = c.newInstance();
         c.getMethod(metnam, new Class[] { }).invoke(o, new Object[] { });
     }
     public static void compileMemoryMemory(String src, String cp, 
String name, SpecialClassLoader xcl, PrintStream err) {
         JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
         DiagnosticCollector<JavaFileObject> diacol = new 
DiagnosticCollector<JavaFileObject>();
         StandardJavaFileManager sjfm = 
javac.getStandardFileManager(diacol, null, null);
         SpecialJavaFileManager xfm = new SpecialJavaFileManager(sjfm, xcl);
         CompilationTask compile = javac.getTask(null, xfm, diacol, 
Arrays.asList(new String[] { "-classpath", cp }), null,
                                                 Arrays.asList(new 
JavaFileObject[] { new MemorySource(name, src) }));
         boolean status = compile.call();
         if(err != null) {
             err.println("Compile status: " + status);
             for(Diagnostic<? extends JavaFileObject> dia : 
diacol.getDiagnostics()) {
                 err.println(dia);
             }
         }
     }
}

class MemorySource extends SimpleJavaFileObject {
     private String src;
     public MemorySource(String name, String src) {
         super(URI.create("string:///" + name.replace(".", "/") + 
".java"), Kind.SOURCE);
         this.src = src;
     }
     public CharSequence getCharContent(boolean ignoreEncodingErrors) {
         return src;
     }
     public OutputStream openOutputStream() {
         throw new IllegalStateException();
     }
     public InputStream openInputStream() {
         return new ByteArrayInputStream(src.getBytes());
     }
}

class MemoryByteCode extends SimpleJavaFileObject {
     private ByteArrayOutputStream baos;
     public MemoryByteCode(String name) {
         super(URI.create("byte:///" + name.replace(".", "/") + 
".class"), Kind.CLASS);
     }
     public CharSequence getCharContent(boolean ignoreEncodingErrors) {
         throw new IllegalStateException();
     }
     public OutputStream openOutputStream() {
         baos = new ByteArrayOutputStream();
         return baos;
     }
     public InputStream openInputStream() {
         throw new IllegalStateException();
     }
     public byte[] getBytes() {
         return baos.toByteArray();
     }
}

class SpecialJavaFileManager extends 
ForwardingJavaFileManager<StandardJavaFileManager> {
     private SpecialClassLoader xcl;
     public SpecialJavaFileManager(StandardJavaFileManager sjfm, 
SpecialClassLoader xcl) {
         super(sjfm);
         this.xcl = xcl;
     }
     public JavaFileObject getJavaFileForOutput(Location location, 
String name, JavaFileObject.Kind kind, FileObject sibling) throws 
IOException {
         name = sibling.getName().substring(1, 
sibling.getName().length() - 5).replace("/", ".");
         MemoryByteCode mbc = new MemoryByteCode(name);
         xcl.addClass(name, mbc);
         return mbc;
     }
}

class SpecialClassLoader extends ClassLoader {
     private Map<String,MemoryByteCode> m;
     public SpecialClassLoader() {
         super(SpecialClassLoader.class.getClassLoader());
         m = new HashMap<String, MemoryByteCode>();
     }
     protected Class<?> findClass(String name) throws 
ClassNotFoundException {
         MemoryByteCode mbc = m.get(name);
         if(mbc != null) {
             return defineClass(name, mbc.getBytes(), 0, 
mbc.getBytes().length);
         } else {
             throw new ClassNotFoundException(name);
         }
     }
     public void addClass(String name, MemoryByteCode mbc) {
         m.put(name, mbc);
     }
}

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Find similar

Thread

Using sun javac to parse java source Alex J <vstrength@gmail.com> - 2011-08-23 13:24 -0700
  Re: Using sun javac to parse java source Arne Vajhøj <arne@vajhoej.dk> - 2011-08-23 19:00 -0400
    Re: Using sun javac to parse java source Lew <lewbloch@gmail.com> - 2011-08-23 17:25 -0700
      Re: Using sun javac to parse java source Arne Vajhøj <arne@vajhoej.dk> - 2011-08-23 21:52 -0400
        Re: Using sun javac to parse java source Lew <lewbloch@gmail.com> - 2011-08-23 20:20 -0700
          Re: Using sun javac to parse java source Arne Vajhøj <arne@vajhoej.dk> - 2011-08-24 19:22 -0400
            Re: Using sun javac to parse java source Lew <lewbloch@gmail.com> - 2011-08-24 21:05 -0700
    Re: Using sun javac to parse java source Sebastian <sebastian@undisclosed.invalid> - 2011-08-24 10:51 +0200
      Re: Using sun javac to parse java source Arne Vajhøj <arne@vajhoej.dk> - 2011-08-24 19:19 -0400

csiph-web