JavaCompiler从JDK 1.6：如何直接写类字节到byte []数组？ [英] JavaCompiler from JDK 1.6: how to write class bytes directly to byte[] array?

问题描述

所以我最近了解到新的 JavaCompiler API 在JDK 1.6中可用。这使得直接从运行代码中编译 String 到 .class 文件非常简单：

  String className =Foo; 
 String sourceCode =...; 
 
 JavaCompiler compiler = ToolProvider.getSystemJavaCompiler（）; 
 
 List< JavaSourceFromString> unitsToCompile = new ArrayList< JavaSourceFromString>（）
 {{
 add（new JavaSourceFromString（className，sourceCode））; 
}}; 
 
 StandardJavaFileManager fileManager = compiler.getStandardFileManager（null，null，null）; 
 compiler.getTask（null，fileManager，null，null，null，unitsToCompile）.call（）; 
 fileManager.close（）; 
 
 ByteArrayOutputStream bos = new ByteArrayOutputStream（）; 
 FileInputStream fis = new FileInputStream（className +.class）; 
 IOUtils.copyStream（fis，bos）; 
 
 return bos.toByteArray（）; 
  

您可以从 JavaSourceFromString Javadoc 。

这将非常方便地在当前工作中编译 sourceCode 到 Foo.class 目录。

：可以直接编译为 byte [] 数组，并避免处理 File I / O的混乱？

解决方案

也许你可以创建自己的 javax.tools.JavaFileManager 实现类，你将返回自己的实现 javax.tools.FileObject ，然后将它写出到内存，而不是磁盘。所以对于你的子类 javax.tools.FileObject Writer openWriter（）throws IOException $ c> java.io.StringWriter 。所有方法都应转换为 String 。

So I recently learned of the new JavaCompiler API available in JDK 1.6. This makes it very simple to compile a String to a .class file directly from running code:

String className = "Foo";
String sourceCode = "...";

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

List<JavaSourceFromString> unitsToCompile = new ArrayList<JavaSourceFromString>() 
    {{ 
         add(new JavaSourceFromString(className, sourceCode)); 
    }};

StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
compiler.getTask(null, fileManager, null, null, null, unitsToCompile).call();
fileManager.close();    

ByteArrayOutputStream bos = new ByteArrayOutputStream();
FileInputStream fis = new FileInputStream(className + ".class");
IOUtils.copyStream(fis, bos);

return bos.toByteArray();

You can grab the source to JavaSourceFromString from the Javadoc.

This will very handily compile sourceCode to Foo.class in the current working directory.

My question is: is it possible to compile straight to a byte[] array, and avoid the messiness of dealing with File I/O altogether?

解决方案

Maybe you could create your own javax.tools.JavaFileManager implementing class where you would return your own implementation of javax.tools.FileObject which would then write it out to memory instead to disk. So for your subclass of javax.tools.FileObject Writer openWriter() throws IOException method you would return a java.io.StringWriter. All the methods should be converted to their String counterparts.

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