com.ideaaedi.component.compile.DynamicClassLoader Maven / Gradle / Ivy
package com.ideaaedi.component.compile;
import lombok.extern.slf4j.Slf4j;
import javax.tools.JavaFileObject;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* 自定义类加载器，用于加载{@link CharSequenceJavaFileObject}实例
*
* @author JustryDeng
* @since 2021/9/20 16:30:44
*/
@Slf4j
public class DynamicClassLoader extends ClassLoader {
/**
* key - CharSequenceJavaFileObject所代表类的全类名
* value - CharSequenceJavaFileObject实例
*/
private final Map javaFileObjectMap = new ConcurrentHashMap<>(16);
/**
* 假设现在我们要调用{@link DynamicClassLoader#findClass(String)}方法，defineClass两个类
* public class TestLogger1
* 和
* public class TestLogger2 extends TestLogger1时，
*
* 当先defineClass的是TestLogger2时，由于TestLogger2中用到了TestLogger1，那么defineClass方法内部就自动调用对TestLogger1的defineClass，
* 此时，调用findClass方法的调用者只收到了TestLogger2的Class实例，如果调用者不知道TestLogger2中有TestLogger1（即：不知道TestLogger1已经被
* defineClass了的话），调用者再主动对TestLogger1进行findClass时，就会因为重复defineClass，而报错：
* Caused by: java.lang.LinkageError: loader (instance of com/ideaaedi/hot/clazz/compile/DynamicClassLoader): attempted duplicate class definition for name: "com/test/TestLogger1"
*
* currDefinedClass参数就是来解决这个问题的
*/
private final Map> currDefinedClass = new ConcurrentHashMap<>(8);
public DynamicClassLoader(ClassLoader parentClassLoader) {
super(parentClassLoader);
}
@Override
protected Class findClass(String classLongName) throws ClassNotFoundException {
CharSequenceJavaFileObject javaFileObject = javaFileObjectMap.get(classLongName);
if (javaFileObject != null) {
byte[] byteCode = javaFileObject.getByteCode();
Class klass = defineClass(classLongName, byteCode, 0, byteCode.length);
log.info("defineClass {} complement.", classLongName);
currDefinedClass.put(classLongName, klass);
return klass;
}
return super.findClass(classLongName);
}
@Override
public InputStream getResourceAsStream(String name) {
if (name.endsWith(JavaFileObject.Kind.CLASS.extension)) {
String classLongNameWithoutSuffix = name.substring(0, name.length() - JavaFileObject.Kind.CLASS.extension.length()).replace('/', '.');
CharSequenceJavaFileObject javaFileObject = javaFileObjectMap.get(classLongNameWithoutSuffix);
if (javaFileObject != null && javaFileObject.getByteCode() != null) {
return new ByteArrayInputStream(javaFileObject.getByteCode());
}
}
return super.getResourceAsStream(name);
}
/**
* 存
*/
public void registerCompiledSource(String classLongName, CharSequenceJavaFileObject javaFileObject) {
javaFileObjectMap.put(classLongName, javaFileObject);
}
/**
* 罗列
*/
public Collection listCharSequenceJavaFileObject() {
return Collections.unmodifiableCollection(javaFileObjectMap.values());
}
/**
* 获取所有已加载的class
* key - 全类名
* value - class实例
*/
public Map> getClasses() throws ClassNotFoundException {
Map> classes = new HashMap<>(16);
for (CharSequenceJavaFileObject byteCode : javaFileObjectMap.values()) {
String classLongName = byteCode.getName();
if (classes.containsKey(classLongName)) {
log.info("classLongName already been defined.");
continue;
}
Class klass = findClass(classLongName);
classes.putAll(currDefinedClass);
classes.put(classLongName, klass);
currDefinedClass.clear();
}
return classes;
}
/**
* 获取所有已加载的class
* key - 全类名
* value - .class文件字节码
*/
public Map getByteCodes() {
Map result = new HashMap<>(javaFileObjectMap.size());
for (Map.Entry entry : javaFileObjectMap.entrySet()) {
result.put(entry.getKey(), entry.getValue().getByteCode());
}
return result;
}
}