从名字上理解，所谓依赖注入，即组件之间的依赖关系由容器在运行期决定，形象的来说，即由容器动态的将某种依赖关系注入到组件之中。
一、构造器注入 之前讲过，点击这里。
二、set注入 (重点) 注意：要求被注入的属性 , 必须有set方法 , set方法的方法名由set + 属性首字母大写 , 如果属性是boolean类型, 没有set方法 , 是 is。 实体类：
package com.liu.pojo; /** * @author liucong * @date 2020/10/6 - 16:40 */ public class Address { private String address; public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "Address{" + "address='" + address + '\'' + '}'; } } package com.liu.pojo; import java.util.*; /** * @author liucong * @date 2020/10/6 - 16:39 */ public class Student { private String name; private Address address; private String[] books; private List<String> hobbies; private Map<String,String> card; private Set<String> games; private String wife; private Properties info; public String getName() { return name; } public void setName(String name) { this.name = name; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } public String[] getBooks() { return books; } public void setBooks(String[] books) { this.books = books; } public List<String> getHobbies() { return hobbies; } public void setHobbies(List<String> hobbies) { this.hobbies = hobbies; } public Map<String, String> getCard() { return card; } public void setCard(Map<String, String> card) { this.card = card; } public Set<String> getGames() { return games; } public void setGames(Set<String> games) { this.games = games; } public String getWife() { return wife; } public void setWife(String wife) { this.wife = wife; } public Properties getInfo() { return info; } public void setInfo(Properties info) { this.info = info; } @Override public String toString() { return "Student{" + "name='" + name + '\'' + ", address=" + address + ", books=" + Arrays.toString(books) + ", hobbies=" + hobbies + ", card=" + card + ", games=" + games + ", wife='" + wife + '\'' + ", info=" + info + '}'; } }1.普通值注入
<bean id="student" class="com.liu.pojo.Student"> <!--第一种，普通值注入，value--> <property name="name" value="小葱"/> </bean>2.Bean注入
<bean id="address" class="com.liu.pojo.Address"> <property name="address" value="西安"/> </bean> <bean id="student" class="com.liu.pojo.Student"> <!--第一种，普通值注入，value--> <property name="name" value="小葱"/> <!--第二种，Bean注入，ref--> <property name="address" ref="address"/> </bean>3.数组注入
<property name="books"> <array> <value>红楼梦</value> <value>西游记</value> <value>水浒传</value> <value>三国演义</value> </array> </property>4.List注入
<property name="hobbies"> <list> <value>听歌</value> <value>敲代码</value> <value>看电影</value> </list> </property>5.Map注入
<property name="card"> <map> <entry key="身份证" value="414566988564"/> <entry key="银行卡" value="145214521456"/> </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">20200525</prop> <prop key="性别">男</prop> <prop key="姓名">小明</prop> </props> </property>三、拓展注入实现
实体类 注意：没有有参构造函数
package com.liu.pojo; /** * @author liucong * @date 2020/10/6 - 20:08 */ public class User { private String name; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "User{" + "name='" + name + '\'' + ", age=" + age + '}'; } }1、p命名空间注入 需要在头文件中加入约束文件
<?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:p="http://www.springframework.org/schema/p" 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.liu.pojo.User" p:name="小葱" p:age="18"/>2、c 命名空间注入 需要在头文件中加入约束文件
<?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:c="http://www.springframework.org/schema/c" xsi:schemaLocation="http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd"> <!--c命名空间注入，通过构造器注入：construct-args--> <bean id="user2" class="com.liu.pojo.User" c:name="liucong" c:age="19" scope="prototype"/>注意：在实体类中需要加入有参构造函数，否则会报错。
