编译HelloWorld成功，因为它只需要它自己的源代码。当您尝试编译ExtendedHelloWorld时，它会失败，因为它需要自己的源代码和HelloWorld的源代码。这可以通过将每个类存储在HashMap<String, String>中来实现，其中key是类名，并且value是类的源代码。
我建议您对代码进行一些更改。
我会压缩你的compile方法并将其分解为两种不同的编译方法。当你想编译一个没有扩展从内存编译的类的类时，第一个会被使用。当你想编译一个扩展从内存编译的类的类时，第二个会被使用。
/*
* Method to compile a class which doesn't extend a class that's been compiled from memory.
*/
public static Class<?> compile(String className, String sourceCode, URLClassLoader classLoader) throws Exception {
return compileHelper(className, classLoader, Arrays.asList(new JavaSourceFromString(className, sourceCode)));
}
/*
* Method to compile a class which extends a class that's been compiled from
* memory.
*
* This method takes in the class name, a Set of Map.Entry<String, String>,
* which contains class names and their sources, and a class loader. This
* method iterates over the entries in the Set, creates JavaFileObjects from
* the class names and their sources and adds each JavaFileObject to an
* ArrayList which will be used in the 'compileHelper' method.
*/
public static Class<?> compile(String className, Set<Map.Entry<String, String>> nameAndSource, URLClassLoader classLoader) throws Exception {
List<JavaFileObject> compilationUnits = new ArrayList<>();
for(Entry<String, String> entry : nameAndSource) {
compilationUnits.add(new JavaSourceFromString(entry.getKey(), entry.getValue()));
}
return compileHelper(className, classLoader, compilationUnits);
}
上述方法然后调用辅助方法，它实际上编译类。此方法与您的compile方法非常相似，但诊断的输出已移至单独的方法printDiagnostics(diagnostics)。
/*
* Helper method that actually does the compiling.
*/
private static Class<?> compileHelper(String className, URLClassLoader classLoader, Iterable<? extends JavaFileObject> compilationUnits) throws Exception {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
CompilationTask task = null;
boolean success = false;
// debug compilation units section
System.out.println("Compiling " + className);
System.out.println(" - compilationUnits ");
for(JavaFileObject o : compilationUnits) {
System.out.println(" + " + o.toString());
}
// end debug
task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
success = task.call();
if (success) {
System.out.println("Successful compilation of " + className);
return Class.forName(className.replace(".", "/"), true, classLoader);
} else {
System.out.println("Failed while compiling " + className);
printDiagnostics(diagnostics);
throw new Exception("It didn't work!");
}
}
为了使用上述方法，你需要使用HashMap<String, String>存储每个要编译的类的类名和源代码。然后，当你准备好编译做出compile电话在entrySet()经过距HashMap，例如：compile(className, nameAndSource.entrySet(), classLoader)
例如：
public static void main(String args[]) throws Exception {
Map<String, String> nameAndSource = new HashMap<>();
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
String className;
StringBuilder sourceCode;
// HelloWorld class
className = "HelloWorld";
sourceCode = new StringBuilder();
sourceCode.append("public class HelloWorld {");
sourceCode.append(" public static void main(String args[]) {");
sourceCode.append(" System.out.append(\"This is in another java file\");");
sourceCode.append(" }");
sourceCode.append("}");
// pass the class name and source code to 'compile'
Class<?> helloWorld = compile(className, sourceCode.toString(), classLoader);
// add HelloWorld class name and source code to HashMap
nameAndSource.put(className, sourceCode.toString());
// ExtendedHelloWorldClass
className = "ExtendedHelloWorld";
sourceCode = new StringBuilder();
sourceCode.append("public class ExtendedHelloWorld extends HelloWorld {");
sourceCode.append(" public int num = 2;");
sourceCode.append("}");
// add ExtendedHelloWorld class name and source code to HashMap
nameAndSource.put(className, sourceCode.toString());
// here's where we pass in the nameAndSource entrySet()
Class<?> extendedHelloWorld = compile(className, nameAndSource.entrySet(), classLoader);
return;
}
这里是完整的源代码是什么我试图描述如上：
public class CompileSourceInMemory {
/*
* Method to compile a class which extends a class that's been compiled from
* memory.
*
* This method takes in the class name, a Set of Map.Entry<String, String>,
* which contains class names and their sources, and a class loader. This
* method iterates over the entries in the Set, creates JavaFileObjects from
* the class names and their sources and adds each JavaFileObject to an
* ArrayList which will be used the private compile method.
*/
public static Class<?> compile(String className, Set<Map.Entry<String, String>> nameAndSource, URLClassLoader classLoader) throws Exception {
List<JavaFileObject> compilationUnits = new ArrayList<>();
for (Entry<String, String> entry : nameAndSource) {
compilationUnits.add(newJavaSourceFromString(entry.getKey(), entry.getValue()));
}
return compileHelper(className, classLoader, compilationUnits);
}
/*
* Method to compile a class which doesn't extend a class that's been
* compiled from memory.
*/
public static Class<?> compile(String className, String sourceCode, URLClassLoader classLoader) throws Exception {
return compileHelper(className, classLoader, Arrays.asList(new JavaSourceFromString(className, sourceCode)));
}
/*
* Helper method that actually does the compiling.
*/
private static Class<?> compileHelper(String className, URLClassLoader classLoader, Iterable<? extends JavaFileObject> compilationUnits) throws Exception {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
CompilationTask task = null;
boolean success = false;
// debug compilation units section
System.out.println("Compiling " + className);
System.out.println(" - compilationUnits ");
for (JavaFileObject o : compilationUnits) {
System.out.println(" + " + o.toString());
}
// end debug
task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
success = task.call();
if (success) {
System.out.println("Successful compilation of " + className);
return Class.forName(className.replace(".", "/"), true, classLoader);
} else {
System.out.println("Failed while compiling " + className);
printDiagnostics(diagnostics);
throw new Exception("It didn't work!");
}
}
public static void main(String args[]) throws Exception {
Map<String, String> nameAndSource = new HashMap<>();
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
String className;
StringBuilder sourceCode;
// HelloWorld Class
className = "HelloWorld";
sourceCode = new StringBuilder();
sourceCode.append("public class HelloWorld {");
sourceCode.append(" public static void main(String args[]) {");
sourceCode.append(" System.out.append(\"This is in another java file\");");
sourceCode.append(" }");
sourceCode.append("}");
// pass the class name and source code to 'compile'
Class<?> helloWorld = compile(className, sourceCode.toString(), classLoader);
// add HelloWorld class name and source code to HashMap
nameAndSource.put(className, sourceCode.toString());
// ExtendedHelloWorld Class
className = "ExtendedHelloWorld";
sourceCode = new StringBuilder();
sourceCode.append("public class ExtendedHelloWorld extends HelloWorld {");
sourceCode.append(" public int num = 2;");
sourceCode.append("}");
// add ExtendedHelloWorld class name and source code to HashMap
nameAndSource.put(className, sourceCode.toString());
// pass the nameAndSource entrySet() to 'compile'
Class<?> extendedHelloWorld = compile(className, nameAndSource.entrySet(), classLoader);
// ExtendedExtendedHelloWorld Class
className = "ExtendedExtendedHelloWorld";
sourceCode = new StringBuilder();
sourceCode.append("public class ExtendedExtendedHelloWorld extends ExtendedHelloWorld {");
sourceCode.append(" public void printNum() { System.out.println(num); }");
sourceCode.append("}");
// add ExtendedExtendedHelloWorld class name and source code to HashMap
nameAndSource.put(className, sourceCode.toString());
// pass the nameAndSource entrySet() to 'compile'
Class<?> extendedExtendedHelloWorld = compile(className, nameAndSource.entrySet(), classLoader);
Object eehw = extendedExtendedHelloWorld.newInstance();
return;
}
private static void printDiagnostics(DiagnosticCollector<JavaFileObject> diagnostics) {
StringBuilder sb = new StringBuilder("-- Diagnostics --\n");
for (Diagnostic<?> d : diagnostics.getDiagnostics()) {
sb.append(String
.format("d.getCode() - %s%nd.getKind() - %s%nd.getPosition() - %d%nd.getStartPosition() - %d%nd.getEndPosition() - %d%nd.getSource() - %s%nd.getMessage(null) - %s%n",
d.getCode(), d.getKind().toString(),
d.getPosition(), d.getStartPosition(),
d.getEndPosition(), d.getSource().toString(),
d.getMessage(null)));
}
System.out.println(sb.append("--").toString());
}
}
class JavaSourceFromString extends SimpleJavaFileObject {
final String code;
JavaSourceFromString(String name, String code) {
super(URI.create("string:///" + name.replace('.', '/')
+ Kind.SOURCE.extension), Kind.SOURCE);
this.code = code;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}
这里是上面运行代码的输出：
Compiling HelloWorld
- compilationUnits
+ JavaSourceFromString[string:///HelloWorld.java]
Successful compilation of HelloWorld
Compiling ExtendedHelloWorld
- compilationUnits
+ JavaSourceFromString[string:///ExtendedHelloWorld.java]
+ JavaSourceFromString[string:///HelloWorld.java]
Successful compilation of ExtendedHelloWorld
Compiling ExtendedExtendedHelloWorld
- compilationUnits
+ JavaSourceFromString[string:///ExtendedHelloWorld.java]
+ JavaSourceFromString[string:///ExtendedExtendedHelloWorld.java]
+ JavaSourceFromString[string:///HelloWorld.java]
Successful compilation of ExtendedExtendedHelloWorld
它不适用于像br.bla.ExtendedHelloWorld这样的全限定类名。 – hbelmiro