java 自定义动态脚本

java 语言自身具有动态性，通过字节码，类加载实现动态性，我们可以实现自己的字节码动态修改，再让jvm 加载。但是源码进行动态加载呢？

就像php,python 这种及时编译，及时运行。（很方便，省去编译）

下面说说我自己用java实现的一套支持java原生态的动态脚本

实现过程

1、源码编译

2、实现类加载load源码，获取class

3、通过反射，执行返回的class

实现源码如下，有简略的注释，希望大家能看懂。。

ScriptHelper //脚本引擎类
ScriptClassLoader //自定义类加载器
Script //脚本源码类

ScriptHelper

package com.usefullc.crawler.common.script;

import com.usefullc.platform.common.utils.MD5Utils;
import org.apache.commons.io.FileUtils;
import org.apache.commons.lang.ClassUtils;
import org.apache.commons.lang.SystemUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

/**
 * Created by shengshan.tang on 8/3/2015 at 2:10 PM
 * 脚本
 */
public class ScriptHelper {

    private  final static Logger log = LoggerFactory.getLogger(ScriptHelper.class);

    public static Map<String,Object> execute(String scriptContent,Map<String,Object> paramMap){
        Map<String,Object> resultMap = new HashMap<String, Object>();
        try {
            //
            String folder = System.getProperty("java.io.tmpdir");
//            String fileId = UUID.randomUUID().toString();
            String basePath = folder + "crawler";
            String sourceFilePath = basePath + File.separator + "source";
            if(new File(sourceFilePath).mkdir()){
                log.info("init create base source folder");
            }
            String fileId = "Script_"+MD5Utils.toMD5(scriptContent);
            String filePath = sourceFilePath + File.separator + fileId+".java";
            log.info("filePath="+filePath);

            //operate source java
            //获取package
            int startIndex = scriptContent.indexOf("package");
            int endIndex = scriptContent.indexOf(";",startIndex);
            String packageStr = scriptContent.substring(startIndex+7,endIndex).trim();
            log.info("packageStr="+packageStr);

            scriptContent = scriptContent.replaceAll("Script",fileId);   //class name replace
            FileUtils.write(new File(filePath),scriptContent,"utf-8");


            //compiler
            String classFilePath = basePath+File.separator+"classs";
            if(new File(classFilePath).mkdir()){
                log.info("init create class folder");
            }
            String libPath = Thread.currentThread().getContextClassLoader().getResource("").getPath();
            log.info("libPath="+libPath);
            libPath = libPath.replace("classes", "lib"); //
            libPath = libPath.substring(1);

            String classPath = "$CLASS_PATH";
            if(SystemUtils.OS_NAME.startsWith("Windows")){
                classPath = "%CLASS_PATH%";
            }

            String cmd = "javac -g -Djava.ext.dirs="+libPath+" -cp "+classPath+" -sourcepath "+sourceFilePath+" -d "+classFilePath+" "+filePath;
            log.info("cmd="+cmd);

            //exeuce compiler
            Process process = Runtime.getRuntime().exec(cmd);
            int exitValue = process.waitFor();
            log.info("exitValue="+exitValue);

            //class loader
            ScriptClassLoader classLoader = new ScriptClassLoader(classFilePath);
            Class scriptClass  = classLoader.findClass(packageStr+"."+fileId);
            Object instance = scriptClass.newInstance();
            Method method = scriptClass.getDeclaredMethod("execute", Map.class);

            method.invoke(instance,paramMap);


        }catch(Exception e){
            e.printStackTrace();
        }
        return resultMap;

    }

    public static void main(String[] args) {
        String sourceStr = "package com.usefullc.crawler.common.script;\n" +
                "\n" +
                "import java.util.Map;\n" +
                "import java.util.Set;\n" +
                "\n" +
                "/**\n" +
                " * Created by shengshan.tang on 8/3/2015 at 3:19 PM\n" +
                " */\n" +
                "public class Script {\n" +
                "\n" +
                "    public void execute(Map<String,Object> paramMap){\n" +
                "        System.out.println(\"test ok!\");\n" +
                "        if(paramMap != null && !paramMap.isEmpty()){\n" +
                "            Set<Map.Entry<String,Object>> entrySet = paramMap.entrySet();\n" +
                "            for(Map.Entry<String,Object>  entry : entrySet){\n" +
                "                System.out.println(entry.getKey()+\"=\"+entry.getValue());\n" +
                "            }\n" +
                "        }\n" +
                "    }\n" +
                "}\n";
        Map<String,Object> paramMap = new HashMap<String, Object>();
        paramMap.put("name","tangshengshan");
        paramMap.put("sex","男");
        execute(sourceStr,paramMap);
    }
}

//

ScriptClassLoader

package com.usefullc.crawler.common.script;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

/**
 * 脚本加载类
 * Created by shengshan.tang on 8/3/2015 at 3:52 PM
 */
public class ScriptClassLoader extends  ClassLoader {

    String classTargetPath;

    public ScriptClassLoader(String classTargetPath) {
        this.classTargetPath = classTargetPath;
    }

    @Override
    protected Class findClass(String name) throws ClassNotFoundException {
        try {
            byte bytes[] = getClassBytes(name);
            Class thisClass = defineClass(name,bytes,0,bytes.length);
            return thisClass;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private byte [] getClassBytes(String className) throws IOException {
        //builder class file path
        className = className.replace('.', File.separatorChar) + ".class";
        String classFilePath = classTargetPath +File.separator+className;
        byte [] bytes = FileUtils.readFileToByteArray(new File(classFilePath));
        return bytes;

    }





}

//

Script

package com.usefullc.crawler.common.script;

import java.util.Map;
import java.util.Set;

/**
 * Created by shengshan.tang on 8/3/2015 at 3:19 PM
 */
public class Script {

    public void execute(Map<String,Object> paramMap){
        System.out.println("test ok!");
        if(paramMap != null && !paramMap.isEmpty()){
            Set<Map.Entry<String,Object>> entrySet = paramMap.entrySet();
            for(Map.Entry<String,Object>  entry : entrySet){
                System.out.println(entry.getKey()+"="+entry.getValue());
            }
        }
    }
}

版权声明：本文为博主原创文章，未经博主允许不得转载。