What are the three ways of spring ioc injection?

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声明:
         该bean类似于javaConfig中的@Bean注解;
         用于创建bean的类通过class属性来指定，并且需要使用全限定的类名。
         通过id指定bean的ID。如果不显示指定，默认使用class的全限定名进行命名。
         eg:
         com.jpeony.spring.common.HelloServiceImpl#0，其#0是一个计数器的形式，
         用来区分相同类型的其他bean。
         使用自动化命名很方便，但是没有多少实际用处，还是建议自己给bean显示设定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;
 
    // 构造方法注入
    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声明:
         该bean类似于javaConfig中的@Bean注解;
         用于创建bean的类通过class属性来指定，并且需要使用全限定的类名。
         通过id指定bean的ID。如果不显示指定，默认使用class的全限定名进行命名。
         eg:
         com.jpeony.spring.common.HelloServiceImpl#0，其#0是一个计数器的形式，
         用来区分相同类型的其他bean。
         使用自动化命名很方便，但是没有多少实际用处，还是建议自己给bean显示设定ID。
     -->
    <bean id="helloService" class="com.jpeony.spring.common.HelloServiceImpl"/>
 
    <!-- 构造方法注入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;
    //年龄
    private String age;
    //方法类
    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 + "岁，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命名标签 -->
       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标签注入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;
    //年龄
    private String age;
    //方法类
    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 + "岁，大家好!");
    }
 
}

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       xmlns:p="http://www.springframework.org/schema/p"
       5e49173f29e4a67ddaa90131e7a99dea
       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">
    
    9df278062f1e81860f65eb12100b2b72

    a9792929f72ef4e41fe56b009215d491
    ...........
    4bb0e59fd50cbfe6f6ce2215b9d94243
 
    1e928befbc0f48f44eec15e59207e744
        093f30557f32572e8ac2e4ba8bcdba31
        30fe8a23ea2fb08456a9dcc68d3d7007
    0cb3faf542ecac6f480b475d17bb9dd0

    ea108911772f997d1c30f6a3a707e315
    516e0c3bf2fb206b6995515c46ebe8c94bb0e59fd50cbfe6f6ce2215b9d94243
 
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