java 动态生成类再编译最后代理

package spring.vhostall.com.proxy;

public interface Store {
    public void sell();
}

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package spring.vhostall.com.proxy;

public class Supermarket implements Store {

    @Override
    public void sell() {
        System.out.println("sel in supermarket.....");
    }
}

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package spring.vhostall.com.proxy;

import java.io.File;
import java.io.FileWriter;
import java.lang.reflect.Constructor;
import java.net.URL;
import java.net.URLClassLoader;

import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

public class Test {
    public static void main(String[] args) throws Exception {
        String rt = "\r\n";
        StringBuilder source = new StringBuilder();
        source.append("package spring.vhostall.com.proxy;" + rt + rt);
        source.append("public class Dealer implements Store" + " {" + rt);
        source.append("    private Store s;" + rt + rt);
        source.append("    public Dealer(Store s) {" + rt);
        source.append("        this.s = s;" + rt);
        source.append("    }" + rt + rt);
        source.append("    public void sell()" + " {" + rt);
        source.append("        System.out.println(\"price markup....\");" + rt);
        source.append("        s.sell();" + rt);
        source.append("    }" + rt);
        source.append("}");

        String fileName = System.getProperty("user.dir")// 获取到项目的根路径
                + "/src/spring/vhostall/com/proxy/Dealer.java";
        File f = new File(fileName);
        FileWriter fw = new FileWriter(f);
        fw.write(source.toString());
        fw.flush();
        fw.close();// 这里只是产生一个JAVA文件,简单的IO操作

        // compile下面开始编译这个Store.java
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        URL[] urls = new URL[] { new URL("file:/"
                + System.getProperty("user.dir") + "/src") };
        URLClassLoader ul = new URLClassLoader(urls);
        Class c = ul.loadClass("spring.vhostall.com.proxy.Dealer");

        // 客户端调用

        Constructor ctr = c.getConstructor(Store.class);
        Store s = (Store) ctr.newInstance(new Supermarket());// 这里看到,这个我们这个代理类必须实现Store的原因
        s.sell();
    }
}