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java - 无法扩展运行时编译的类

转载 作者:行者123 更新时间:2023-11-30 02:50:24 25 4
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我用过this answer作为在运行时编译类的引用并且它可以正常工作。所以现在我需要扩展实际上找不到的编译类。

我已经尝试过这个:

import java.io.File;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;

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

public class CompileSourceInMemory {

public static Class<?> compile(String className, String sourceCode, URLClassLoader classLoader) throws Exception {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();

JavaFileObject file = new JavaSourceFromString(className, sourceCode);

Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
CompilationTask task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);

boolean success = task.call();

for (Diagnostic<?> diagnostic : diagnostics.getDiagnostics()) {
System.out.println(diagnostic.getCode());
System.out.println(diagnostic.getKind());
System.out.println(diagnostic.getPosition());
System.out.println(diagnostic.getStartPosition());
System.out.println(diagnostic.getEndPosition());
System.out.println(diagnostic.getSource());
System.out.println(diagnostic.getMessage(null));
}

System.out.println("Success: " + success);

if (success) {
return Class.forName(className.replace(".", "/"), true, classLoader);
} else {
throw new Exception("Didn't work!");
}
}

public static void main(String args[]) throws Exception {
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
StringBuilder sourceCode = new StringBuilder();
// sourceCode.append("package br.bla;");
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("}");
Class<?> helloWorld = compile("HelloWorld", sourceCode.toString(), classLoader);

sourceCode = new StringBuilder();
// sourceCode.append("package br.bla;");
sourceCode.append("public class ExtendedHelloWorld extends HelloWorld {");
sourceCode.append(" public int i = 2;");
sourceCode.append("}");

Class<?> extendedHelloWorld = compile("ExtendedHelloWorld", sourceCode.toString(), classLoader);
Object object = extendedHelloWorld.newInstance();

return;
}
}

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;
}
}

输出是:

Success: true
compiler.err.cant.resolve
ERROR
40
40
50
JavaSourceFromString[string:///ExtendedHelloWorld.java]
cannot find symbol
symbol: class HelloWorld
Success: false

有人知道如何编译我的 ExtendedHelloWorld 类吗?

最佳答案

编译HelloWorld成功是因为它只需要自己的来源。当您尝试编译ExtendedHelloWorld时它失败了,因为它需要自己的源代码和 HelloWorld的来源。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,value是类的源代码。

<小时/>

我建议对您的代码进行一些更改。

我会放气你的compile方法并将其分解为两种不同的编译方法。当您想要编译一个不扩展从内存编译的类的类时,将使用第一个。当您确实想要编译一个扩展从内存编译的类的类时,将使用第二个。

/*
* 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);
}

上述方法然后调用一个实际编译类的辅助方法。此方法与您的 compile 非常相似方法,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,您需要使用 HashMap<String, String>存储您要编译的每个类的类名和源代码。然后,当您准备好编译时,请调用 compile传入entrySet()来自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;
}
<小时/>

这是我上面尝试描述的完整源代码:

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;
}
}

这是运行上面代码的输出:

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

关于java - 无法扩展运行时编译的类,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38857990/

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