The three ways of spring ioc injection are: 1. Setter method injection. After the container instantiates the bean by calling the parameterless constructor or parameterless static factory method, it calls the setter method of the bean. 2. Constructor method injection. 3. P namespace injection.

#The operating environment of this tutorial: windows7 system, java8 version, Dell G3 computer.

Spring IOC (three methods of dependency injection):

1. Setter method injection

Setter method injection is when the container instantiates a bean by calling a parameterless constructor or a parameterless static factory method, and then calls the setter method of the bean, which implements setter-based dependency injection.

package com.jpeony.spring.setter;
import com.jpeony.spring.common.HelloServiceImpl;public class HelloWord {
private HelloService helloService;
 
    // setter方式注入Bean
    public void setHelloService(HelloService helloService) {
        this.helloService = helloService;
    }
 
    @Override
    public void selfIntroduction() {
        // 向大家打招呼
        helloService.sayHello("大家好!");
    }
 
}

<?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聲明:
         該bean類似于javaConfig中的@Bean注解;
         用于創(chuàng)建bean的類通過class屬性來指定，并且需要使用全限定的類名。
         通過id指定bean的ID。如果不顯示指定，默認(rèn)使用class的全限定名進(jìn)行命名。
         eg:
         com.jpeony.spring.common.HelloServiceImpl#0，其#0是一個(gè)計(jì)數(shù)器的形式，
         用來區(qū)分相同類型的其他bean。
         使用自動(dòng)化命名很方便，但是沒有多少實(shí)際用處，還是建議自己給bean顯示設(shè)定ID。
     -->
    <bean id="helloService" class="com.jpeony.spring.common.HelloServiceImpl"/>
 
    <!-- setter注入bean -->
    <bean id="HelloWord" class="com.jpeony.spring.setter.HelloWord">
        <property name="helloService" ref="helloService"/>
    </bean>
 
</beans>

2. Constructor injection

Constructor dependency injection is implemented by triggering the constructor of a class through the container. The class has a series of Parameters, each parameter represents a dependency on other classes.

package com.jpeony.spring.setter;
import com.jpeony.spring.common.HelloServiceImpl;

public class HelloWord {
    private HelloService helloService;
 
    // 構(gòu)造方法注入
    public HelloWord (HelloService helloService) {
        this.helloService = helloService;
    }
 
}

<?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聲明:
         該bean類似于javaConfig中的@Bean注解;
         用于創(chuàng)建bean的類通過class屬性來指定，并且需要使用全限定的類名。
         通過id指定bean的ID。如果不顯示指定，默認(rèn)使用class的全限定名進(jìn)行命名。
         eg:
         com.jpeony.spring.common.HelloServiceImpl#0，其#0是一個(gè)計(jì)數(shù)器的形式，
         用來區(qū)分相同類型的其他bean。
         使用自動(dòng)化命名很方便，但是沒有多少實(shí)際用處，還是建議自己給bean顯示設(shè)定ID。
     -->
    <bean id="helloService" class="com.jpeony.spring.common.HelloServiceImpl"/>
 
    <!-- 構(gòu)造方法注入bean -->
    <bean id="HelloWord" class="com.jpeony.spring.setter.HelloWord">
        <constructor-arg><ref bean="helloService"/></constructor-arg>
    </bean>
 
</beans>

3. P namespace injection

package com.jpeony.spring.setter;
import com.jpeony.spring.common.HelloServiceImpl;

public class HelloWord {
    //名字
    private String name;
    //年齡
    private String age;
    //方法類
    private HelloService helloService;
 
    public void setName (String name) {
        this.name = name;
    }
    
    public void setAge (String age) {
        this.age = age;
    }
    
    public void setHelloService(HelloService helloService) {
        this.helloService = helloService;
    }
 
    @Override
    public void selfIntroduction() {
        // 向大家打招呼
        helloService.sayHello("我叫"+ name + "，今年" + age + "歲，大家好!");
    }
 
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       <!-- 引入p命名標(biāo)簽 -->
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
    <bean id="helloService" class="com.jpeony.spring.common.HelloServiceImpl"/>
 
    <!-- p標(biāo)簽注入bean -->
    <bean id="HelloWord" class="com.jpeony.spring.setter.HelloWord" 
     p:name="明明" p:age="24" p:helloService-ref="helloService"></bean>
 
</beans>

P tag injection collection bean

package com.jpeony.spring.setter;
import com.jpeony.spring.common.HelloServiceImpl;
import java.util.List;

public class HelloWord {
    //名字
    private String name;
    //年齡
    private String age;
    //方法類
    private List<HelloService> helloServices;
 
    public void setName (String name) {
        this.name = name;
    }
    
    public void setAge (String age) {
        this.age = age;
    }
    
    public void setHelloServices(List<HelloService> helloServices) {
        this.helloServices = helloServices;
    }
 
    @Override
    public void selfIntroduction() {
        // 向大家打招呼
        helloServices[0].sayHello("我叫"+ name + "，今年" + age + "歲，大家好!");
    }
 
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       <!-- 引入p命名標(biāo)簽 -->
       xmlns:p="http://www.springframework.org/schema/p"
       <!-- 引入util命名標(biāo)簽 -->
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
    <bean id="helloService" class="com.jpeony.spring.common.HelloServiceImpl"/>

    <bean id="helloService2" class="com.jpeony.spring.common.HelloServiceImpl">
    ...........
    </bean>
 
    <util:list id="helloServices">
        <ref bean="helloService"/>
        <ref bean="helloService2"/>
    </util:list>

    <!-- p標(biāo)簽注入bean -->
    <bean id="HelloWord" class="com.jpeony.spring.setter.HelloWord" 
     p:name="明明" p:age="24" p:helloServices-ref="helloServices"></bean>
 
</beans>

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