初学Spring

1.首先我们先建立一个java项目，导入spring相关的jar包

jar包自行下载，上面只是截一部分的。

2.1 准备pojo

package cn.yf.pojo;

public class Person {
    
    private int age;
    private String name;
    
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Person [age=" + age + ", name=" + name + "]";
    }
    
}

2.2 按照常规方法创建对象

package cn.yf.test;

import cn.yf.pojo.Person;

public class Test1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Person person = new Person();
        person.setAge(20);
        person.setName("tht");
        System.out.println(person.getAge());
        System.out.println(person.getName());
    }

}

运行结果：

20
tht

2.3 用spring来创建对象

首先在src下创建applicationContext.xml，它是spring的核心配置文件

applicationContext.xml的内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop 
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx 
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context      
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
 
    <bean name="p" class="cn.yf.pojo.Person">
        <property name="age" value="20"></property>
        <property name="name" value="tht"></property>
    </bean>
 
</beans>

里面的黑色字体是配置：<bean>配置需要创建的对象，name用于之后从spring容器获得实例时使用的，class需要创建实例的全限定类名，property用于配置属性，name是属性名，value是属性值

创建SpringTest1

package cn.yf.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.yf.pojo.Person;

public class TestSpring1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
        Person p = (Person)context.getBean("p");
        System.out.println(p.getAge());
        System.out.println(p.getName());
    }

}

运行结果如下：

20
tht

和上面一样。

3 spring注入对象

我们建立一个新的类，但是这个类要用到别的对象

package cn.yf.pojo;

public class Father {
    
    private int age;
    private String name;
    private Person person;
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Person getPerson() {
        return person;
    }
    public void setPerson(Person person) {
        this.person = person;
    }
    @Override
    public String toString() {
        return "Father [age=" + age + ", name=" + name + ", person=" + person + "]";
    }
    
    
    
}

编写测试类如下：

package cn.yf.test;

import cn.yf.pojo.Father;
import cn.yf.pojo.Person;

public class Test2 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Person person = new Person();
        person.setAge(20);
        person.setName("tht");
        Father father = new Father();
        father.setAge(50);
        father.setName("yf");
        father.setPerson(person);
        System.out.println(father.getAge());
        System.out.println(father.getName());
        System.out.println(father.getPerson());
    }

}

结果：

50
yf
Person [age=20, name=tht]

这就是我们通常方法，现在看来好像没什么，但是一旦对象个数多了，耦合性就会过高，spring就是来解决这种问题的。

spring方法实现：

首先配置applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop 
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx 
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context      
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
 
    <bean name="p" class="cn.yf.pojo.Person">
        <property name="age" value="20"></property>
        <property name="name" value="tht"></property>
    </bean>
    
    <bean name="f" class="cn.yf.pojo.Father">
        <property name="age" value="50"></property>
        <property name="name" value="yf"></property>
        <property name="person" ref="p"></property>
    </bean>
 
</beans>

上面红色字体就是对Father类的配置，里面的对象注入要用ref

编写测试代码

package cn.yf.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.yf.pojo.Father;

public class TestSpring2 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
        Father father = (Father)context.getBean("f");
        System.out.println(father.getAge());
        System.out.println(father.getName());
        System.out.println(father.getPerson());
    }

}

结果和上面一样

50
yf
Person [age=20, name=tht]

这样就借助spring实现具有依赖关系的对象之间的解耦

4 spring注解方式IOC/DI

4.1 @Autowired

首先一样的我们先配置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"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop 
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx 
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context      
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
     
     <context:annotation-config/>
     <!-- 告诉Spring要用注解的方式进行配置 -->
    <bean name="p" class="cn.yf.pojo.Person">
        <property name="age" value="20"></property>
        <property name="name" value="tht"></property>
    </bean>
    
    <bean name="f" class="cn.yf.pojo.Father">
        <property name="age" value="50"></property>
        <property name="name" value="yf"></property>
        <!-- <property name="person" ref="p"></property> -->
    </bean>

黑色这一行的功能在后面由注解来完成

修改Father类

@Autowired
private Person person;

也可以这样修改

@Autowired
public void setPerson(Person person) {
        this.person = person;
}

结果都是一样的

50
yf
Person [age=20, name=tht]

4.2 @Resource

效果和@Autowired一样，它们都是对注入对象行为的注解，效果一样都为

50
yf
Person [age=20, name=tht]

4.3 @Component

一样的先对applicationContext.xml进行配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop 
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx 
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context      
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
     
     <context:component-scan base-package="cn.yf.pojo"></context:component-scan>
 
</beans>

作用是告诉spring，bean都放在cn.yf.pojo这个包下面

然后对Person类进行修改

@Component("p")
public class Person

对Father类的配置

@Component("f")
public class Father

然后再次运行测试代码结果如下：

0
null
Person [age=0, name=null]

因为没有设置初值，所以默认为0或者null

 5.1 Spring AOP

什么是AOP：面向切面编程，利用AOP可以对业务逻辑的各个部分进行隔离，从而使得业务逻辑各个部分之间的耦合度降低，提高程序的可重用性，同时提高了开发的效率。

先设计业务类代码如下

package cn.yf.service;

import org.springframework.stereotype.Component;

@Component("s")
public class ProductService {
    
    public void doSomeService(){
        System.out.println("doSomeService");
    }    
    
}

再设计辅助功能类（切面）

package cn.yf.aspect;

import org.aspectj.lang.ProceedingJoinPoint;

public class LoggerAspect {
    
    public Object log(ProceedingJoinPoint joinPoint) throws Throwable{
        System.out.println("start log:" + joinPoint.getSignature().getName());
        //用于执行核心功能的代码
        Object object = joinPoint.proceed();
        System.out.println("end log:" + joinPoint.getSignature().getName());
        return object;
    }
    
}

配置applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop 
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx 
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context      
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
     
     <!-- 声明业务对象 -->
     <bean name="s" class="cn.yf.service.ProductService"></bean>
     <!-- 声明日志切面 -->
     <bean id="loggerAspect" class="cn.yf.aspect.LoggerAspect"></bean>
     
     <aop:config>
         <!-- 指定核心业务 -->
         <aop:pointcut expression="execution(* cn.yf.service.ProductService.*(..))" id="loggerCutpoint"/>
         <!-- 指定辅助业务 -->
         <aop:aspect id="logAspect" ref="loggerAspect">
             <aop:around pointcut-ref="loggerCutpoint" method="log"/>
         </aop:aspect>
     </aop:config>
     
</beans>

测试代码：

package cn.yf.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.yf.service.ProductService;

public class TestSpring3 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        ApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
        ProductService s = (ProductService)context.getBean("s");
        s.doSomeService();
    }

}

测试结果：

start log:doSomeService
doSomeService
end log:doSomeService

 5.2 Spring注解方式AOP

使用@Component("s") 注解ProductService 类

@Component("s")
public class ProductService

注解配置切面

@Aspect
@Component
public class LoggerAspect {
    
    @Around(value = "execution(* cn.yf.service.ProductService.*(..))")
    public Object log(ProceedingJoinPoint joinPoint) throws Throwable{
        System.out.println("start log:" + joinPoint.getSignature().getName());
        //用于执行核心功能的代码
        Object object = joinPoint.proceed();
        System.out.println("end log:" + joinPoint.getSignature().getName());
        return object;
    }
    
}

对applicationContext.xml进行配置

<context:component-scan base-package="cn.yf.aspect"></context:component-scan>
     <context:component-scan base-package="cn.yf.service"></context:component-scan>
     <aop:aspectj-autoproxy/>

运行结果一样：

start log:doSomeService
doSomeService
end log:doSomeService