Question

问题的背景：
创建一个包含具有不存在的超类的类的java文件;获取javac解析类，但不编译它;以编程方式生成超类（这意味着没有类文件）;最后让javac成功生成一个类文件。

这是CompilerAPITest.java

import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.util.Arrays;
import java.util.Locale;
import java.util.logging.Logger;
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;    
import javax.tools.JavaCompiler.CompilationTask;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

/**
* A test class to test dynamic compilation API.
*
*/
public class CompilerAPITest {
    static final Logger logger = Logger.getLogger(CompilerAPITest.class.getName()) ;

    public void doCompilation (){
        File[] files = {new File("/home/guestu/GeneratedClass.java")};

        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

        StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, Locale.getDefault(), null);
        /* Prepare a list of compilation units (java source code file objects) to input to  compilation task*/
        Iterable<? extends JavaFileObject> compilationUnits = stdFileManager.getJavaFileObjects(files);

        /*Create a diagnostic controller, which holds the compilation problems*/
        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
        /*Create a compilation task from compiler by passing in the required input objects prepared above*/
        CompilationTask compilerTask = compiler.getTask(null, stdFileManager, diagnostics, null, null, compilationUnits) ;

        boolean status = compilerTask.call();
        if (!status){//If compilation error occurs
            /*Iterate through each compilation problem and print it*/
            for (Diagnostic diagnostic : diagnostics.getDiagnostics()){
                System.out.format("Error on line %d in %s", diagnostic.getLineNumber(), diagnostic);
            } 
    }
    try {
       stdFileManager.close() ;//Close the file manager
    } catch (IOException e) {
 }

//Here is Helloworld.java
public class Helloworld extends GeneratedClass{
    public static void main(String[] args){
        System.out.println("Hello");

    }

}

//And here is GeneratedClass.java
package com.sun.tools.javac.parser;

import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.tree.JCTree.JCAnnotation;
import com.sun.tools.javac.tree.JCTree.JCClassDecl;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.tree.JCTree.JCExpression;
import com.sun.tools.javac.tree.JCTree.JCModifiers;
import com.sun.tools.javac.tree.JCTree.JCTypeParameter;
import com.sun.tools.javac.util.List;
import com.sun.tools.javac.util.ListBuffer;
import com.sun.tools.javac.util.Name;
import com.sun.tools.javac.util.Names;

/* This class programmatically produces the superclass "GeneratedClass" with signature public class GeneratedClass{} */

public class GeneratedClass {
    TreeMaker maker;
    Names names;
    public GeneratedClass(ParserFactory fac) {
        maker = fac. F;
        names = fac.names;
    }

    public JCCompilationUnit getTree() {
        ListBuffer<JCTree> defs = new ListBuffer<JCTree>();
        defs.append(makeClassDecl());
        return maker.TopLevel(List.<JCAnnotation>nil(), null, defs.toList());
    }

    /* This is a class decalaration node for public class GeneratedClass{}*/
    protected JCClassDecl makeClassDecl() {
        JCModifiers mods = maker.Modifiers(Flags.PUBLIC);
        Name name = names.fromString("GeneratedClass");
        return maker.ClassDef(mods, name, List.<JCTypeParameter>nil(), null, List.<JCExpression>nil(), List.<JCTree>nil());
    }
}

我当前的挑战

我以编程方式生成了一个类文件（GeneratedClass）。我希望它能被java编译器选中以编译Helloworld.java。我已经尝试了上面的方法但是Helloworld没有编译，因为它无法获取GeneratedClass。有没有办法可以做到这一点？谢谢你的时间。

Answer 1

我猜你必须自定义文件管理器。但是你的任务似乎非常适合注释处理器。代码将被解析，如果缺少某些类，则完全没问题。解析后的代码模型将传递给注释处理器，注释处理器可以执行任何选择。甚至还有一些用于编写生成的类的基础结构。参见

http://docs.oracle.com/javase/7/docs/api/javax/annotation/processing/Processor.html

和

http://deors.wordpress.com/2011/10/08/annotation-processors/

让Javac拿起我的班级

1 个答案: