java代码片段执行

我发现 XXL-JOB 有 GLUE 功能，粘合了多种语言。

1、引入 maven 依赖

<!-- groovy-all -->
<dependency>
    <groupId>org.codehaus.groovy</groupId>
    <artifactId>groovy</artifactId>
    <version>3.0.10</version>
</dependency>

2、自测一版

// 2022-09-15 14:40   测试 String Java 代码 -> 对象
public static void main1(String[] args) throws Exception {
    String code = "package com.xxl.job.service.handler;\n" +
            "\n" +
            "import com.xxl.job.core.context.XxlJobHelper;\n" +
            "import com.xxl.job.core.handler.IJobHandler;\n" +
            "\n" +
            "public class DemoGlueJobHandler extends IJobHandler {\n" +
            "\n" +
            "\t@Override\n" +
            "\tpublic void execute() throws Exception {\n" +
            "      System.out.println(\"abc\");\n" +
            "\t}\n" +
            "\n" +
            "}\n";
    IJobHandler handler = GlueFactory.getInstance().loadNewInstance(code);
    handler.execute();
}


// 2022-09-15 14:42   测试 自定义 Java 代码 -> 反射调用方法
public static void main(String[] args) throws Exception {
    String code = "            package com.xxl.job.service.handler;\n" +
            "            \n" +
            "            import com.xxl.job.core.context.XxlJobHelper;\n" +
            "            import com.xxl.job.core.handler.IJobHandler;\n" +
            "            \n" +
            "            public class A {\n" +
            "            \n" +
            "                public String b() throws Exception {\n" +
            "                  System.out.println(\"abc\");\n" +
            "                  return \"bbb\";\n" +
            "                }\n" +
            "                \n" +
            "            }";

    GroovyClassLoader gcl = new GroovyClassLoader();
    Class<?> clazz = gcl.parseClass(code);
    Object a = clazz.newInstance();
    Method b = clazz.getDeclaredMethod("b");
    Object bbb = b.invoke(a);
}

3、这里放出一下 XXL-JOB 2.3.1 中使用到 GroovyClassLoader 的源码

package com.xxl.job.core.glue;

import com.xxl.job.core.glue.impl.SpringGlueFactory;
import com.xxl.job.core.handler.IJobHandler;
import groovy.lang.GroovyClassLoader;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * glue factory, product class/object by name
 *
 * @author xuxueli 2016-1-2 20:02:27
 */
public class GlueFactory {


    private static GlueFactory glueFactory = new GlueFactory();
    public static GlueFactory getInstance(){
        return glueFactory;
    }
    public static void refreshInstance(int type){
        if (type == 0) {
            glueFactory = new GlueFactory();
        } else if (type == 1) {
            glueFactory = new SpringGlueFactory();
        }
    }


    /**
     * groovy class loader
     */
    private GroovyClassLoader groovyClassLoader = new GroovyClassLoader();
    private ConcurrentMap<String, Class<?>> CLASS_CACHE = new ConcurrentHashMap<>();

    /**
     * load new instance, prototype
     *
     * @param codeSource
     * @return
     * @throws Exception
     */
    public IJobHandler loadNewInstance(String codeSource) throws Exception{
        if (codeSource!=null && codeSource.trim().length()>0) {
            Class<?> clazz = getCodeSourceClass(codeSource);
            if (clazz != null) {
                Object instance = clazz.newInstance();
                if (instance!=null) {
                    if (instance instanceof IJobHandler) {
                        this.injectService(instance);
                        return (IJobHandler) instance;
                    } else {
                        throw new IllegalArgumentException(">>>>>>>>>>> xxl-glue, loadNewInstance error, "
                                + "cannot convert from instance["+ instance.getClass() +"] to IJobHandler");
                    }
                }
            }
        }
        throw new IllegalArgumentException(">>>>>>>>>>> xxl-glue, loadNewInstance error, instance is null");
    }
    private Class<?> getCodeSourceClass(String codeSource){
        try {
            // md5
            byte[] md5 = MessageDigest.getInstance("MD5").digest(codeSource.getBytes());
            String md5Str = new BigInteger(1, md5).toString(16);

            Class<?> clazz = CLASS_CACHE.get(md5Str);
            if(clazz == null){
                clazz = groovyClassLoader.parseClass(codeSource);
                CLASS_CACHE.putIfAbsent(md5Str, clazz);
            }
            return clazz;
        } catch (Exception e) {
            return groovyClassLoader.parseClass(codeSource);
        }
    }

    /**
     * inject service of bean field
     *
     * @param instance
     */
    public void injectService(Object instance) {
        // do something
    }

}