Java JavaCompiler.run()也编译匿名类
我正在尝试动态加载文本文件并编译它们Java JavaCompiler.run()也编译匿名类,java,classloader,dynamic-loading,javacompiler,Java,Classloader,Dynamic Loading,Javacompiler,我正在尝试动态加载文本文件并编译它们 File file = new File("Files/"+fileName+".java"); JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); compiler.run(null, null, errStream, file.getAbsolutePath()); 随后,我将加载编译后的.class文件: public Class loadStrategyClass(File
File file = new File("Files/"+fileName+".java");
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
compiler.run(null, null, errStream, file.getAbsolutePath());
随后,我将加载编译后的.class文件:
public Class loadStrategyClass(File strategyClassFile) throws IOException
{
FileChannel roChannel = new RandomAccessFile(strategyClassFile, "r").getChannel();
ByteBuffer buffer = roChannel.map(FileChannel.MapMode.READ_ONLY, 0, (int)roChannel.size());
return defineClass(strategyClassFile.getName(), buffer, (ProtectionDomain)null);
}
我目前遇到两个问题:
第一个是我加载的.java文件是否包含匿名类。JavaCompiler类似乎不会编译这些。
线程“main”java.lang.IllegalAccessException中出现异常:Class Loader.ClassLoader无法使用修饰符访问类文件.myname.myclass$1的成员
第二点:
有时我会因为NoClassDefFoundError而出错:
线程“main”java.lang.NoClassDefFoundError中出现异常:Files/myname/myclass
尽管其他类将正确加载并且.class文件位于该路径中。显然,您的
loadStrategyClass
是在自定义类加载器中定义的。问题是,仅仅对您感兴趣的类调用一次defineClass
是不够的,您的类加载器必须能够根据需要解析类,通常是通过实现findClass
,这样JVM就可以解析依赖项,比如内部类
您没有指定如何获取loadStrategyClass
方法的strategyClassFile
参数。由于您在没有任何选项的情况下运行编译器,我想您只需查找相对于源文件的文件。要解析其他依赖项,需要知道类目录的实际根。当您定义类文件的存储位置时,它会变得更容易,例如
// customize these, if you want, null triggers default behavior
DiagnosticListener<JavaFileObject> diagnosticListener = null;
Locale locale = null;
JavaCompiler c = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager fm
= c.getStandardFileManager(diagnosticListener, locale, Charset.defaultCharset());
// define where to store compiled class files - use a temporary directory
Path binaryDirectory = Files.createTempDirectory("compile-test");
fm.setLocation(StandardLocation.CLASS_OUTPUT,
Collections.singleton(binaryDirectory.toFile()));
JavaCompiler.CompilationTask task = c.getTask(null, fm,
diagnosticListener, Collections.emptySet(), Collections.emptySet(),
// to make this a stand-alone example, I use embedded source code
Collections.singleton(new SimpleJavaFileObject(
URI.create("string:///Class1.java"), Kind.SOURCE) {
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return "package test;\npublic class Class1 { public class Inner {} }";
}
}));
if(task.call()) try {
URLClassLoader cl = new URLClassLoader(new URL[]{ binaryDirectory.toUri().toURL() });
Class<?> loadedClass = cl.loadClass("test.Class1");
System.out.println("loaded "+loadedClass);
System.out.println("inner classes: "+Arrays.toString(loadedClass.getClasses()));
} catch(ClassNotFoundException ex) {
ex.printStackTrace();
}
如果您使用它来动态绑定插件或模块,您可以扩展搜索以查找实现特定接口或具有特定注释的结果类。是否需要特定java代码,或者是否可以使用嵌入式脚本来执行像nashorn这样的操作?按您所指的语言环境:?这似乎是一个地理区域,这似乎是错误的;它链接到所使用的所有其他类型。如果底层编译器支持,Locale
参数允许本地化错误消息。谢谢。这是如何工作的:)。我在网上找不到任何描述我想要什么的东西。
public static Class<?> compile(
DiagnosticListener<JavaFileObject> diagnosticListener,
Locale locale, String sourceFile) throws IOException, ClassNotFoundException {
JavaCompiler c = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager fm
= c.getStandardFileManager(diagnosticListener, locale, Charset.defaultCharset());
// define where to store compiled class files - use a temporary directory
Path binaryDirectory = Files.createTempDirectory("compile-test");
fm.setLocation(StandardLocation.CLASS_OUTPUT,
Collections.singleton(binaryDirectory.toFile()));
JavaCompiler.CompilationTask task = c.getTask(null, fm,
diagnosticListener, Collections.emptySet(), Collections.emptySet(),
fm.getJavaFileObjects(new File(sourceFile)));
if(task.call()) {
Class<?> clazz = null;
URLClassLoader cl = new URLClassLoader(new URL[]{binaryDirectory.toUri().toURL()});
for(JavaFileObject o: fm.list(
StandardLocation.CLASS_OUTPUT, "", Collections.singleton(Kind.CLASS), true)) {
String s = binaryDirectory.toUri().relativize(o.toUri()).toString();
s = s.substring(0, s.length()-6).replace('/', '.');
clazz = cl.loadClass(s);
while(clazz.getDeclaringClass() != null) clazz = clazz.getDeclaringClass();
if(Modifier.isPublic(clazz.getModifiers())) break;
}
if(clazz != null) return clazz;
throw new ClassNotFoundException(null,
new NoSuchElementException("no top level class generated"));
}
throw new ClassNotFoundException(null,
new NoSuchElementException("compilation failed"));
}