代理模式

简介

结构型模式，通过对真实对象的多一层包装，可以完成很多操作，比如：统计性能、判断权限、记录日志等等。

示例

public interface Subject {
    void doSomeThing();
}

public class RealSubject implements Subject{
    @Override
    public void doSomeThing() {
        System.out.println("real subject do some thing");
    }
}

public class SubjectProxy implements Subject {
    private Subject subject;

    public SubjectProxy(Subject subject) {
        this.subject = subject;
    }

    @Override
    public void doSomeThing() {
        //添加扩展功能，比如统计耗时
        long bg = System.currentTimeMillis();
        subject.doSomeThing();
        long end = System.currentTimeMillis();
        System.out.println("耗时：" + (end - bg));
    }
}

调用

@Test
public void tt(){
	Subject subject = new SubjectProxy(new RealSubject());
	subject.doSomeThing();
}