DI 依赖注入(Dependency Injection)【spring基础】

1、构造器注入

    <bean id="user" class="com.wang.pojo.User">
        <!--方式一-->
        <!--        <constructor-arg index="0" value="王野"/>-->
        <!--方式二,不建议使用，如果有多个参数，-->
        <!--        <constructor-arg type="java.lang.String" value="邢敏"/>-->
        <constructor-arg name="name" value="hfsdjhflkads"/>
    </bean>

2、Set方式注入(重点)

• 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

2. 真实测试对象

3. 测试pojo类 :

   Address.java

    public class Address {
    
        private String address;
    
        public String getAddress() {
            return address;
       }
    
        public void setAddress(String address) {
            this.address = address;
       }
    }
   

   Student.java

    package com.wang.pojo;
    
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    import java.util.Set;
    
    public class Student {
    
        private String name;
        private Address address;
        private String[] books;
        private List<String> hobbys;
        private Map<String,String> card;
        private Set<String> games;
        private String wife;
        private Properties info;
    
        public void setName(String name) {
            this.name = name;
       }
    
        public void setAddress(Address address) {
            this.address = address;
       }
    
        public void setBooks(String[] books) {
            this.books = books;
       }
    
        public void setHobbys(List<String> hobbys) {
            this.hobbys = hobbys;
       }
    
        public void setCard(Map<String, String> card) {
            this.card = card;
       }
    
        public void setGames(Set<String> games) {
            this.games = games;
       }
    
        public void setWife(String wife) {
            this.wife = wife;
       }
    
        public void setInfo(Properties info) {
            this.info = info;
       }
    
        public void show(){
            System.out.println("name="+ name
                    + ",address="+ address.getAddress()
                    + ",books="
           );
            for (String book:books){
                System.out.print("<<"+book+">>	");
           }
            System.out.println("
   爱好:"+hobbys);
    
            System.out.println("card:"+card);
    
            System.out.println("games:"+games);
    
            System.out.println("wife:"+wife);
    
            System.out.println("info:"+info);
    
       }
    }
   

   1、常量注入

    <bean id="student" class="com.wang.pojo.Student">
        <property name="name" value="小明"/>
    </bean>
   

   测试：

    @Test
    public void test01(){
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
    
        Student student = (Student) context.getBean("student");
    
        System.out.println(student.getName());
    
    }
   

   2、Bean注入

   注意点：这里的值是一个引用，ref

    <bean id="addr" class="com.kuang.pojo.Address">
        <property name="address" value="重庆"/>
    </bean>
    
    <bean id="student" class="com.kuang.pojo.Student">
        <property name="name" value="小明"/>
        <property name="address" ref="addr"/>
    </bean>
   

   3、数组注入

    <bean id="student" class="com.wang.pojo.Student">
        <property name="name" value="小明"/>
        <property name="address" ref="addr"/>
        <property name="books">
            <array>
                <value>西游记</value>
                <value>红楼梦</value>
                <value>水浒传</value>
            </array>
        </property>
    </bean>
   

   4、List注入

    <property name="hobbys">
        <list>
            <value>听歌</value>
            <value>看电影</value>
            <value>爬山</value>
        </list>
    </property>
   

   5、Map注入

    <property name="card">
        <map>
            <entry key="中国邮政" value="456456456465456"/>
            <entry key="建设" value="1456682255511"/>
        </map>
    </property>
   

   6、set注入

    <property name="games">
        <set>
            <value>LOL</value>
            <value>BOB</value>
            <value>COC</value>
        </set>
    </property>
   

   7、Null注入

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

   8、Properties注入

    <property name="info">
        <props>
            <prop key="学号">20234343</prop>
            <prop key="性别">男</prop>
            <prop key="姓名">小fd</prop>
        </props>
    </property>
   

3、其他方式

记得有参构造和无参构造器写上

1、P命名空间注入 : 需要在头文件中加入约束文件

 导入约束 : xmlns:p="http://www.springframework.org/schema/p"
 
 <!--P(属性: properties)命名空间 , 属性依然要设置set方法-->
 <bean id="user" class="com.kuang.pojo.User" p:name="hh" p:age="18"/>

2、c 命名空间注入 : 需要在头文件中加入约束文件

 导入约束 : xmlns:c="http://www.springframework.org/schema/c"
 <!--C(构造: Constructor)命名空间 , 属性依然要设置set方法-->
 <bean id="user" class="com.kuang.pojo.User" c:name="oo" c:age="18"/>

Idea可以自动导入约束

    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("userbeans.xml");
        User user = context.getBean("user", User.class);
        System.out.println(user);
    }
    @Test
    public void test1(){
        ApplicationContext context = new ClassPathXmlApplicationContext("userbeans.xml");
        User user = context.getBean("user2", User.class);
        System.out.println(user);
    }