依赖注入

1、构造器注入

参考IoC创建对象的方式

2、Set方式注入

依赖注入：Set注入

• 依赖：bean对象的创建依赖于容器
• 注入：bean对象中的所有属性，由容器来注入

环境搭建：

1、复杂类型

package com.sw.pojo;

/**
 * @Author suaxi
 * @Date 2020/12/14 16:32
 */
public class Adress {
    private String adress;

    public String getAdress() {
        return adress;
    }

    public void setAdress(String adress) {
        this.adress = adress;
    }
}

2、真实测试对象

package com.sw.pojo;

import java.util.*;

/**
 * @Author suaxi
 * @Date 2020/12/14 16:32
 */
public class Student {
    private String name;
    private Adress adress;
    private String[] books;
    private List<String> hobbys;
    private Map<String,String> card;
    private Set<String> games;
    private String wife;
    private Properties info;
    
    ……
}

3、beans.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="student" class="com.sw.pojo.Student">
        <!--普通值注入 value-->
        <property name="name" value="孙笑川"/>
    </bean>
</beans>

4、测试类

import com.sw.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @Author suaxi
 * @Date 2020/12/14 16:38
 */
public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
    }
}

beans.xml补充：

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="address" class="com.sw.pojo.Address">
        <property name="address" value="昆明"/>
    </bean>

    <bean id="student" class="com.sw.pojo.Student">
        <!--普通值注入 value-->
        <property name="name" value="孙笑川"/>
        <!--bean注入 ref-->
        <property name="address" ref="address"/>

        <!--数组-->
        <property name="books">
            <array>
                <value>高数一</value>
                <value>英语一</value>
                <value>毛概</value>
            </array>
        </property>

        <!--list-->
        <property name="hobbys">
            <list>
                <value>跑步</value>
                <value>游泳</value>
                <value>听音乐</value>
            </list>
        </property>

        <!--map-->
        <property name="card">
            <map>
                <entry key="身份证" value="12345678"/>
                <entry key="银行卡" value="87654321"/>
            </map>
        </property>

        <!--set-->
        <property name="games">
            <set>
                <value>LOL</value>
                <value>FF14</value>
                <value>CSGO</value>
            </set>
        </property>

        <!--null-->
        <property name="wife">
            <null/>
        </property>

        <!--properties-->
        <property name="info">
            <props>
                <prop key="姓名">孙笑川</prop>
                <prop key="学号">123</prop>
                <prop key="性别">男</prop>
            </props>
        </property>
    </bean>
</beans>

3、拓展方式注入

可以使用p命名空间和c命名空间

<?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:p="http://www.springframework.org/schema/p"
       xmlns:c="http://www.springframework.org/schema/c"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <!--p命名空间注入，可以直接注入属性的值：property-->
    <bean id="user" class="com.sw.pojo.User" p:id="1" p:name="孙笑川"/>

    <!--c命名空间注入，通过构造器注入constructor-args-->
    <bean id="user1" class="com.sw.pojo.User" c:id="2" c:name="刘波"/>
</beans>

注：使用前需导入xml约束

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

4、bean的作用域

1、单例模式（Spring默认）

<bean id="user1" class="com.sw.pojo.User" c:id="2" c:name="刘波" scope="singleton"/>

@Test
public void test1(){
    ApplicationContext context = new ClassPathXmlApplicationContext("userBeans.xml");
    User user1 = (User) context.getBean("user");
    User user2 = (User) context.getBean("user");
    System.out.println(user1==user2); //true
}

2、原型模式：每次从容器中get的时候都会产生一个新对象

<bean id="user1" class="com.sw.pojo.User" c:id="2" c:name="刘波" scope="prototype"/>

@Test
public void test1(){
    ApplicationContext context = new ClassPathXmlApplicationContext("userBeans.xml");
    User user1 = (User) context.getBean("user1");
    User user2 = (User) context.getBean("user1");
    System.out.println(user1.hashCode()); //838411509
    System.out.println(user2.hashCode()); //1434041222
    System.out.println(user1==user2); //false
}

3、其余的request、session、application在web开发中使用