package classload;

import javax.tools.*;

import java.io.*;

import java.net.URI;

import java.net.URL;

import java.net.URLClassLoader;

import java.nio.CharBuffer;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Map;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

/**

* Required JDK >= 1.6<br><br>

* This class can help you create the Java byte code dynamically through the string and load it into memory.<br><br>

* <p>

* HOW TO:<br>

* First step. <code>Map<String, byte[]> bytecode = DynamicLoader.compile("TestClass.java", javaSrc);</code><br>

* Second step. <code>DynamicLoader.MemoryClassLoader classLoader = new DynamicLoader.MemoryClassLoader(bytecode);</code><br>

* Third step. <code>Class clazz = classLoader.loadClass("TestClass");</code><br>

* <br>

* Then just like the normal use of the call this class can be.

*/

public class DynamicLoader {

/**

* auto fill in the java-name with code, return null if cannot find the public class

*

* @param javaSrc source code string

* @return return the Map, the KEY means ClassName, the VALUE means bytecode.

*/

public static Map<String, byte[]> compile(String javaSrc) {

Pattern pattern = Pattern.compile("public\\s+class\\s+(\\w+)");

Matcher matcher = pattern.matcher(javaSrc);

if (matcher.find())

return compile(matcher.group(1) + ".java", javaSrc);

return null;

}

/**

* @param javaName the name of your public class,eg: <code>TestClass.java</code>

* @param javaSrc source code string

* @return return the Map, the KEY means ClassName, the VALUE means bytecode.

*/

public static Map<String, byte[]> compile(String javaName, String javaSrc) {

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

StandardJavaFileManager stdManager = compiler.getStandardFileManager(null, null, null);

try (MemoryJavaFileManager manager = new MemoryJavaFileManager(stdManager)) {

JavaFileObject javaFileObject = manager.makeStringSource(javaName, javaSrc);

JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, null, null, Arrays.asList(javaFileObject));

if (task.call())

return manager.getClassBytes();

} catch (IOException e) {

e.printStackTrace();

}

return null;

}

public static class MemoryClassLoader extends URLClassLoader {

Map<String, byte[]> classBytes = new HashMap<String, byte[]>();

public MemoryClassLoader() {

super(new URL[0], MemoryClassLoader.class.getClassLoader());

}

/**

* 需要 className,与对应的流 然后defineClass生成类 defineClass可以在任何方法内生成 例如findClass or loadClass等

*

* @param classBytes

*/

public void add(Map<String, byte[]> classBytes) {

this.classBytes.putAll(classBytes);

}

@Override

protected Class<?> findClass(String name) throws ClassNotFoundException {

byte[] buf = classBytes.get(name);

if (buf == null) {

return super.findClass(name);

}

classBytes.remove(name);

return defineClass(name, buf, 0, buf.length);

}

}

public static class MemoryClassLoader2 extends ClassLoader {

Map<String, byte[]> classBytes = new HashMap<String, byte[]>();

public void add(Map<String, byte[]> classBytes) {

this.classBytes.putAll(classBytes);

}

@Override

public Class<?> loadClass(String name) throws ClassNotFoundException {

System.out.println("1:" + name);

Class<?> c = findLoadedClass(name);

System.out.println("c:" + c);

return super.loadClass(name);

}

@Override

protected Class<?> findClass(String name) throws ClassNotFoundException {

byte[] buf = classBytes.get(name);

if (buf == null) {

return super.findClass(name);

}

classBytes.remove(name);

//defineClass 会走loadClass但不会走 但不会走父加载器循环

return defineClass(name, buf, 0, buf.length);

}

}

}