Java动态编译优化——URLClassLoader 内存泄漏问题解决

import javax.tools.*;
import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;

public class DynamicCompile {
    private URLClassLoader parentClassLoader;
    private String classpath;
    public DynamicCompile() {
        this.parentClassLoader = (URLClassLoader) this.getClass().getClassLoader();
        this.buildClassPath();// 存在动态安装的问题，需要动态编译类路径
    }

    private void buildClassPath() {
        this.classpath = null;
        StringBuilder sb = new StringBuilder();
        for (URL url : this.parentClassLoader.getURLs()) {
            String p = url.getFile();
            sb.append(p).append(File.pathSeparator); //路径分割符linux为:window系统为;
        }
        this.classpath = sb.toString();
    }
    /**
     * 编译出类
     *
     * @param fullClassName 全路径的类名
     * @param javaCode      java代码
     *
     * @return 目标类
     */
    public Class<?> compileToClass(String fullClassName, String javaCode) throws Exception {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
        ClassFileManager fileManager = new ClassFileManager(compiler.getStandardFileManager(diagnostics, null, null));

        List<JavaFileObject> jfiles = new ArrayList<>();
        jfiles.add(new CharSequenceJavaFileObject(fullClassName, javaCode));

        List<String> options = new ArrayList<>();
        options.add("-encoding");
        options.add("UTF-8");
        options.add("-classpath");
        options.add(this.classpath);

        JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, options, null, jfiles);
        boolean success = task.call();

        if (success) {
            JavaClassObject jco = fileManager.getJavaClassObject();
            DynamicClassLoader dynamicClassLoader = new DynamicClassLoader(this.parentClassLoader);
            //加载至内存
            return dynamicClassLoader.loadClass(fullClassName, jco);
        } else {
            for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
                String error = compileError(diagnostic);
                throw new RuntimeException(error);
            }
            throw new RuntimeException("compile error");
        }
    }

    private String compileError(Diagnostic diagnostic) {
        StringBuilder res = new StringBuilder();
        res.append("LineNumber:[").append(diagnostic.getLineNumber()).append("]\n");
        res.append("ColumnNumber:[").append(diagnostic.getColumnNumber()).append("]\n");
        res.append("Message:[").append(diagnostic.getMessage(null)).append("]\n");
        return res.toString();
    }
}

this.parentClassLoader = (URLClassLoader) this.getClass().getClassLoader();

new CharSequenceJavaFileObject(fullClassName, javaCode)

package com.yunerp.web.util.run.compile;

import org.apache.log4j.Logger;
import sun.misc.ClassLoaderUtil;

import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.ToolProvider;
import java.io.File;

import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;


public class DynamicEngine {

    private final Logger log = Logger.getLogger(this.getClass().getName());


    /**
     * @MethodName	: 创建classpath
     * @Description
     */
    private String buildClassPath() {
        StringBuilder sb = new StringBuilder();
        URLClassLoader parentClassLoader = (URLClassLoader) this.getClass().getClassLoader();
        for (URL url : parentClassLoader.getURLs()) {
            String p = url.getFile();
            sb.append(p).append(File.pathSeparator);
        }
        return sb.toString();
    }

    /**
     * @param fullClassName 类名
     * @param javaCode      类代码
     * @return Object
     * @throws IllegalAccessException
     * @throws InstantiationException
     * @MethodName    : 编译java代码到Object
     * @Description
     */
    public Class javaCodeToObject(String fullClassName, final String javaCode) throws IllegalAccessException, InstantiationException {

        DynamicClassLoader dynamicClassLoader = null;
        ClassFileManager fileManager = null;
        List<JavaFileObject> jfiles = null;
        JavaClassObject jco = null;
        URLClassLoader urlClassLoader = null;
        try {
            //获取系统编译器
            JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
            
            // 建立DiagnosticCollector对象
            DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
            //设置系统属性
            System.setProperty("useJavaUtilZip", "true");
            // 建立用于保存被编译文件名的对象
            // 每个文件被保存在一个从JavaFileObject继承的类中
            fileManager = new ClassFileManager(compiler.getStandardFileManager(diagnostics, null, null));

            jfiles = new ArrayList<>();
            jfiles.add(new CharSequenceJavaFileObject(fullClassName, javaCode));

            //使用编译选项可以改变默认编译行为。编译选项是一个元素为String类型的Iterable集合
            List<String> options = new ArrayList<>();
            options.add("-encoding");
            options.add("UTF-8");
            options.add("-classpath");
            //获取系统构建路径
            options.add(buildClassPath());
            //不使用SharedNameTable （jdk1.7自带的软引用，会影响GC的回收，jdk1.9已经解决）
            options.add("-XDuseUnsharedTable");
            //设定使用javaUtilZip，避免zipFileIndex泄漏
            options.add("-XDuseJavaUtilZip");

            JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, options, null, jfiles);

            // 编译源程序
            boolean success = task.call();

            if (success) {
                //如果编译成功，用类加载器加载该类
                jco = fileManager.getJavaClassObject();
                URL[] urls = new URL[]{new File("").toURI().toURL()};
                //获取类加载器（每一个文件一个类加载器）
                urlClassLoader = new URLClassLoader(urls, Thread.currentThread().getContextClassLoader());
                dynamicClassLoader = new DynamicClassLoader(urlClassLoader);
                Class clazz = dynamicClassLoader.loadClass(fullClassName, jco);
                return clazz;
            } else {
                log.error("编译失败: "+ fullClassName);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                //卸载ClassLoader所加载的类
                if (dynamicClassLoader != null) {
                    dynamicClassLoader.close();
                    ClassLoaderUtil.releaseLoader(dynamicClassLoader);
                }
                if (urlClassLoader != null) {
                    urlClassLoader.close();
                }
                if (fileManager != null) {
                    fileManager.flush();
                    fileManager.close();
                }
                if (jco != null) {
                    jco.close();
                }
                jfiles = null;
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}