Spring框架核心之AOP前置知识

傷城~ 2022-08-28 12:42 155阅读 0赞

### 前置知识之代理模式 ###

代理模式就是为其他对象提供一个代理对象，以控制或者增强目标对象  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16]

#### 准备 ####

创建 maven 工程，pom.xml如下

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>org.spring.ss</groupId>
        <artifactId>spring03-proxy</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <properties>
            <maven.compiler.source>8</maven.compiler.source>
            <maven.compiler.target>8</maven.compiler.target>
            <java.version>1.8</java.version>
            <spring.verson>5.3.9</spring.verson>
            <junit.version>5.7.2</junit.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.junit.jupiter</groupId>
                <artifactId>junit-jupiter-engine</artifactId>
                <version>${junit.version}</version>
                <scope>test</scope>
            </dependency>
        </dependencies>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.2</version>
                </plugin>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.1</version>
                    <configuration>
                        <source>${maven.compiler.source}</source>
                        <target>${maven.compiler.target}</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    
    </project>

创建接口

package org.spring.ss.service;
    
    public interface ISomeService { 
        public String doSome(String msg);
    
        public String doSome2(String name, String msg);
    }

创建实现类

package org.spring.ss.service.impl;
    
    import org.spring.ss.service.ISomeService;
    
    public class SomeService implements ISomeService { 
        @Override
        public String doSome(String msg) { 
            System.out.println("目标对象执行了。。。");
            return msg;
        }
    
        @Override
        public String doSome2(String name, String msg) { 
            System.out.println("不代理");
            return msg;
        }
    }

#### 静态代理 ####

直接将代理对象声明出来，容易理解，但是不够灵活。

package org.spring.ss;
    
    import org.spring.ss.service.ISomeService;
    
    public class StaticSomeProxy implements ISomeService { 
        // 需要增强的目标对象
        private ISomeService someService;
    
        public StaticSomeProxy(ISomeService target) { 
            this.someService = target;
        }
    
        @Override
        public String doSome(String msg) { 
            System.out.println("目标对象执行之前的操作");
            String s = this.someService.doSome(msg);
            System.out.println("目标对象执行之后的操作");
            return s.toUpperCase();
        }
    
        @Override
        public String doSome2(String name, String msg) { 
            return null;
        }
    }

添加测试方法

package org.spring.ss;
    
    import org.junit.jupiter.api.Test;
    import org.spring.ss.service.ISomeService;
    import org.spring.ss.service.impl.SomeService;
    
    public class ProxyTest { 
    
        @Test
        public void doSomeTest1() { 
            ISomeService target = new SomeService();
            ISomeService proxy = new org.spring.ss.StaticSomeProxy(target);
            String nihao = proxy.doSome("nihao");
            System.out.println(nihao);
        }
    
    }

执行结果：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16 1]

#### 动态代理之JDK的实现 ####

如果目标实现的有接口，那么我们就可以使用JDK代理模式。  
直接在测试方法中使用。

package org.spring.ss;
    
    import org.junit.jupiter.api.Test;
    import org.spring.ss.service.ISomeService;
    import org.spring.ss.service.impl.SomeService;
    
    import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.Method;
    import java.lang.reflect.Proxy;
    
    public class ProxyTest { 
    
        @Test
        public void doSomeTest2() { 
            ISomeService target = new SomeService();
            ISomeService proxy = (ISomeService) Proxy.newProxyInstance(
                    target.getClass().getClassLoader(),  // 类加载器
                    target.getClass().getInterfaces(),   // 目标对象实现的接口数组
                    /* * 当代理对象执行相关方法的时候，会执行的逻辑 * */
                    new InvocationHandler() { 
                        @Override
                        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
                            // 调用目标对象的方法
                            System.out.println("目标对象执行之前的操作");
                            String msg = (String) method.invoke(target, args[0]);
                            System.out.println("目标对象执行之后的操作");
                            return msg.toUpperCase();
                        }
                    }
            );
    
    
            String nihao = proxy.doSome("nihao");
            System.out.println(nihao);
        }
    }

执行结果：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_19_color_FFFFFF_t_70_g_se_x_16]

#### 动态代理之cglib ####

如果目标对象没有实现任何的接口那么我们是使用不了`JDK`动态代理的，那么这个时候我们只能使用`CGLIB`代理。`CGLIB`的本质其实的代理类继承了目标对象，并重写相关方法。

引入`CGLIB`的依赖

<dependency>
        <groupId>cglib</groupId>
        <artifactId>cglib</artifactId>
        <version>3.3.0</version>
    </dependency>

创建代理类

package org.spring.ss.proxy;
    
    import net.sf.cglib.proxy.Enhancer;
    import net.sf.cglib.proxy.MethodInterceptor;
    import net.sf.cglib.proxy.MethodProxy;
    import org.spring.ss.service.impl.SomeService;
    
    import java.lang.reflect.Method;
    
    public class CglibProxy implements MethodInterceptor { 
        private SomeService target;
    
        public CglibProxy(SomeService target) { 
            this.target = target;
        }
    
        // 创建代理对象
        public SomeService createProxy() { 
            Enhancer enhancer = new Enhancer();
            // 指定父类
            enhancer.setSuperclass(SomeService.class);
            // 指定回调方法
            enhancer.setCallback(this);
            // 创建代理对象
            return (SomeService) enhancer.create();
    
        }
    
        // 需要执行具体的代理方法
        @Override
        public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { 
            System.out.println("before...");
            System.out.println(method.getName());
            String msg = (String) method.invoke(target, objects[0]);
            System.out.println("after...");
            return msg.toUpperCase();
        }
    }

添加测试。

package org.spring.ss;
    
    import org.junit.jupiter.api.Test;
    import org.spring.ss.proxy.CglibProxy;
    import org.spring.ss.service.ISomeService;
    import org.spring.ss.service.impl.SomeService;
    
    public class ProxyTest { 
    
        @Test
        public void doSomeByCglibProxyTest() { 
            ISomeService target = new CglibProxy(new SomeService()).createProxy();
            System.out.println(target.doSome("haha,hello , lilei"));
    // System.out.println(target.doSome2("aa", "haha,hello , lilei222"));
        }
    }

执行结果  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16 2]

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[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220828/293db0e1500a45778fd97219e3b3c4ef.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_19_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/40d0ec74a2504dfab1339d9bf57cfba3.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16 2]: /images/20220828/bb769ca0f08a4a52b3d51a56a33254eb.png