Spring 入门

示例

首先举个栗子，演示 Spring 的注入，项目工程视图如下

定义一个Tutorial类

package com.ggli.aop.model;public class Tutorial {    private String name;    private String url;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getUrl() {        return url;    }    public void setUrl(String url) {        this.url = url;    }    public void printName() {        System.out.println("Tutorial name: " + this.name);    }    public void printUrl() {        System.out.println("Tutorial url: " + this.url);    }    public void printThrowException() {        throw new IllegalArgumentException();    }}

在关联 Spring 的 applicationContext.xml 中配置 bean

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="tutorial1" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Java Essential Training"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>    </bean>    <bean id="tutorial2" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Overview of IDEs for Java"/>        <property name="url" value="https://www.lynda.com/Development-Tools-tutorials/Overview-IDEs-Java/486760-2.html"/>    </bean>    <bean id="tutorial3" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Up and Running with Java Applications"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Up-Running-Java-Applications/435790-2.html"/>    </bean></beans>

使用 p 简化 bean 的属性赋值（convert to p-namespace）
首先，导入 p 的命名空间（不需要导入 xsi:schemaLocation）

xmlns:p="http://www.springframework.org/schema/p"

bean 定义就可以写为

<bean id="tutorial1" class="com.ggli.aop.model.Tutorial" p:name="Java Essential Training" p:url="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>

新建一个单元测试类

import com.ggli.aop.model.Tutorial;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class UnitTest {    @Test    public void testObject() {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Tutorial tutorial = (Tutorial) context.getBean("tutorial1");        System.out.println("------------------------------");        tutorial.printName();        tutorial.printUrl();        System.out.println("------------------------------");        try {            tutorial.printThrowException();        } catch (Exception e) {        }    }}

静态工厂方法配置 bean

Java 程序源码

package com.ggli.aop.fatory;import java.util.HashMap;import java.util.Map;public class StaticFactoryMethod {    public static Map<String, Tutorial> map = new HashMap<String, Tutorial>();    static {        map.put("Alice", new Tutorial(        "Java Essential Training",        "https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"));        map.put("Grace", new Tutorial(        "Overview of IDEs for Java",        "https://www.lynda.com/Development-Tools-tutorials/Overview-IDEs-Java/486760-2.html"));    }    public static Tutorial getTutorial(String key){        return map.get(key);    }}

xml 配置

<!-- static factory method -->    <bean id="tutorial" factory-method="getTutorial" class="com.ggli.aop.fatory.StaticFactoryMethod">    <constructor-arg value="Alice" type="java.lang.String"></constructor-arg></bean>

实例工厂方法配置 bean

Java 程序源码

package com.ggli.aop.fatory;import java.util.HashMap;import java.util.Map;public class InstanceFactoryMethod {    public static Map<String, Tutorial> map = new HashMap<String, Tutorial>();    static {        map.put("Alice", new Tutorial(        "Java Essential Training",        "https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"));        map.put("Grace", new Tutorial(        "Overview of IDEs for Java",        "https://www.lynda.com/Development-Tools-tutorials/Overview-IDEs-Java/486760-2.html"));    }    public static Tutorial getTutorial(String key){        return map.get(key);    }}

xml 配置

<!-- instance factory method --><bean id="method" class="com.ggli.aop.fatory.InstanceFactoryMethod"/><bean id="tutorial" factory-bean="method" factory-method="getTutorial" class="com.ggli.aop.fatory.StaticFactoryMethod">    <constructor-arg value="Alice"></constructor-arg></bean>

AOP

Spring AOP 相当于一个拦截器，当一个方法执行时，Spring能够拦截正在执行的方法，在方法执行前或后增加额外的功能和处理。

Spring AOP 支持4种类型的通知

Type Description before advice 在方法执行前执行 after returning advice 在方法执行返回一个结果后执行 after throwing advice 在方法执行中抛出异常时执行 around advice 在方法执行前后和抛出异常时执行，综合了上述三种

下面分别介绍。

before advice

创建一个实现 MethodBeforeAdvice 接口的类，该类实现 before 方法，当被拦截的方法执行前，该 before 方法会被执行。

package com.ggli.aop.advice;import org.springframework.aop.MethodBeforeAdvice;import java.lang.reflect.Method;public class BeforeAdvice implements MethodBeforeAdvice {    public void before(Method method, Object[] objects, Object o) throws Throwable {        System.out.println("[Before method] " + o.getClass().getName() + "." + method.getName() + "()");    }}

在 Spring 的 applicationContext.xml 中，创建BeforeAdvice类对应的 bean，以及一个代理的 bean
设置两个 property

• target：设置要拦截的 bean
• interceptorNames：设置作用于 proxy/target 上的通知

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="tutorial1" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Java Essential Training"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>    </bean>    <bean id="beforeAdvice" class="com.ggli.aop.advice.BeforeAdvice"/>    <bean id="proxy1" class="org.springframework.aop.framework.ProxyFactoryBean">        <property name="target" ref="tutorial1"/>        <property name="interceptorNames">            <list>                <value>beforeAdvice</value>            </list>        </property>    </bean></beans>

after advice

创建一个实现 AfterReturningAdvice 接口的类，在被拦截的方法运行返回结果后将执行类中的 afterReturning 方法

package com.ggli.aop.advice;import org.springframework.aop.AfterReturningAdvice;import java.lang.reflect.Method;public class AfterAdvice implements AfterReturningAdvice {    public void afterReturning(Object o, Method method, Object[] objects, Object o1) throws Throwable {        System.out.println("[After method] " + o1.getClass().getName() + "." + method.getName() + "()");    }}

修改 applicationContext.xml 文件

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="tutorial1" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Java Essential Training"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>    </bean>    <bean id="beforeAdvice" class="com.ggli.aop.advice.BeforeAdvice"/>    <bean id="afterAdvice" class="com.ggli.aop.advice.AfterAdvice"/>    <bean id="proxy1" class="org.springframework.aop.framework.ProxyFactoryBean">        <property name="target" ref="tutorial1"/>        <property name="interceptorNames">            <list>                <value>beforeAdvice</value>                <value>afterAdvice</value>            </list>        </property>    </bean></beans>

after throwing advice

创建一个类实现 ThrowsAdvice 接口。

package com.ggli.aop.advice;import org.springframework.aop.ThrowsAdvice;public class ExceptionAdvice implements ThrowsAdvice {    public void afterThrowing(IllegalArgumentException e) throws Throwable {        System.out.println("[ExceptionAdvice] sends the regards: " + e.toString());    }}

修改 applicationContext.xml 文件

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="tutorial1" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Java Essential Training"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>    </bean>    <bean id="beforeAdvice" class="com.ggli.aop.advice.BeforeAdvice"/>    <bean id="afterAdvice" class="com.ggli.aop.advice.AfterAdvice"/>    <bean id="exceptionAdvice" class="com.ggli.aop.advice.ExceptionAdvice"/>    <bean id="proxy1" class="org.springframework.aop.framework.ProxyFactoryBean">        <property name="target" ref="tutorial1"/>        <property name="interceptorNames">            <list>                <value>beforeAdvice</value>                <value>afterAdvice</value>                <value>exceptionAdvice</value>            </list>        </property>    </bean></beans>

around advice

创建一个类实现 MethodInterceptor 接口，需要在方法中执行 Object result = methodInvocation.proceed() 方法才能得到执行，否则方法不会执行。

package com.ggli.aop.advice;import org.aopalliance.intercept.MethodInterceptor;import org.aopalliance.intercept.MethodInvocation;public class AroundAdvice implements MethodInterceptor {    public Object invoke(MethodInvocation methodInvocation) throws Throwable {        try {            System.out.println("[Around method] Before: " + methodInvocation.getMethod().getName());            Object obj = methodInvocation.proceed();            System.out.println("[Around method] After: " + methodInvocation.getMethod().getName());            return obj;        } catch (IllegalArgumentException e) {            System.out.println("[Around method] Exception: " + methodInvocation.getMethod().getName());            throw e;        }    }}

修改 applicationContext.xml 文件

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="tutorial1" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Java Essential Training"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Java-Essential-Training/377484-2.html"/>    </bean>    <bean id="tutorial2" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Overview of IDEs for Java"/>        <property name="url" value="https://www.lynda.com/Development-Tools-tutorials/Overview-IDEs-Java/486760-2.html"/>    </bean>    <bean id="tutorial3" class="com.ggli.aop.model.Tutorial">        <property name="name" value="Up and Running with Java Applications"/>        <property name="url" value="https://www.lynda.com/Java-tutorials/Up-Running-Java-Applications/435790-2.html"/>    </bean>    <bean id="beforeAdvice" class="com.ggli.aop.advice.BeforeAdvice"/>    <bean id="afterAdvice" class="com.ggli.aop.advice.AfterAdvice"/>    <bean id="exceptionAdvice" class="com.ggli.aop.advice.ExceptionAdvice"/>    <bean id="aroundAdvice" class="com.ggli.aop.advice.AroundAdvice"/>    <bean id="proxy1" class="org.springframework.aop.framework.ProxyFactoryBean">        <property name="target" ref="tutorial2"/>        <property name="interceptorNames">            <list>                <value>beforeAdvice</value>                <value>afterAdvice</value>                <value>exceptionAdvice</value>            </list>        </property>    </bean>    <bean id="proxy2" class="org.springframework.aop.framework.ProxyFactoryBean">        <property name="target" ref="tutorial3"/>        <property name="interceptorNames">            <list>                <value>aroundAdvice</value>            </list>        </property>    </bean></beans>

单元测试类

import com.ggli.aop.model.Tutorial;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class UnitTest {    @Test    public void testObject() {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Tutorial tutorial = (Tutorial) context.getBean("tutorial1");        tutorial.printName();        System.out.println("------------------------------");        tutorial.printUrl();        System.out.println("------------------------------");        try {            tutorial.printThrowException();        } catch (Exception e) {        }    }    @Test    public void testAdvice() {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Tutorial tutorial = (Tutorial) context.getBean("proxy1");        tutorial.printName();        System.out.println("------------------------------");        tutorial.printUrl();        try {            tutorial.printThrowException();        } catch (Exception e) {        }    }    @Test    public void testAround() {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Tutorial tutorial = (Tutorial) context.getBean("proxy2");        tutorial.printName();        System.out.println("------------------------------");        tutorial.printUrl();        try {            tutorial.printThrowException();        } catch (Exception e) {        }    }}