1.构造器函数注入

分为无参构造方法和有参构造方法两种方式，其中有参构造方法又包含三种方式。
有参构造的三种方式：

1. 下标赋值
2. 参数类型赋值
3. 参数名赋值

案例：

User.java

public class User {private String name;private String mess;public User(String name,String mess){this.name=name;this.mess=mess;}public void setName(String name) {this.name = name;}public void setMess(String mess) {this.mess = mess;}public String getName() {return name;}public String getMess() {return mess;}public void show(){System.out.println("name="+name+"   "+"mess="+mess);}
}

UserE.java

public class UserE {private String name;public UserE(){System.out.println("UserE创建了");}public void setName(String name) {this.name = name;}public String getName() {return name;}}

UserT.java

public class UserT {private String name;public UserT(String name){this.name=name;}public void setName(String name) {this.name = name;}public String getName() {return name;}public void show(){System.out.println("name="+name);}
}

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/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"><!--IOC有参构造方法创建对象(构造器注入) constructor-arg --><!--1. 下标赋值--><!--<bean id="user" class="com.hui.pojo.User"><constructor-arg index="0" value="李家辉"/><constructor-arg index="1" value="李家毅"/></bean>--><!--2. 通过类型创建(不建议使用，多个参数类型一样时会出错)--><!--<bean id="user" class="com.hui.pojo.User"><constructor-arg type="java.lang.String" value="李家辉"/></bean>--><!--3. 直接通过参数名赋值(重点掌握)--><bean id="user" class="com.hui.pojo.User"><constructor-arg name="name" value="李家辉1"/><constructor-arg name="mess" value="李家毅1"/></bean><bean id="userT" class="com.hui.pojo.UserT" name="t,userT2 userT3;userT4"><constructor-arg name="name" value="T"/></bean><!--bean的介绍：id: bean的唯一标识符，也就是相当于对象名class: bean对象所对应的全限定名 ：包名 + 类型name: 也是别名，而且比alias更加高级，可以同时取多个别名，而且别名之间的分隔符可以是不相同的--><bean id="userE" class="com.hui.pojo.UserE"></bean><!--取别名，添加了别名，不一定必须使用别名，可以继续使用原来的id--><alias name="user" alias="user2"/></beans>

MyTest.java

public class MyTest {public static void main(String[] args) {/*** IOC创建对象的方式：* 1. 使用无参构造方法创建对象。默认！* 2. 使用有参构造方法创建对象。*    a. 下标赋值*    b. 参数类型赋值(不建议使用，当出现多个参数类型一直时，会出错)*    c. 参数名赋值(重点掌握)** spring容器相当于婚介网站，对象已经存在(bean)，想要结婚直接get，在配置文件加载的时候，容器中管理的对象就已经初始化了* 配置文件加载时，优先加载无参构造的bean，然后按照从上到下的顺序再加载有参构造的bean，此例是：先加载UserE类的bean，然后加载User类的bean，最后是UserT* */ApplicationContext context=new ClassPathXmlApplicationContext("beans.xml");User user= (User) context.getBean("user2");user.show();UserT userT= (UserT) context.getBean("userT2");userT.show();}
}

运行结果：

2.Setter方法注入（重点）

被注入的属性必须有set方法，Setter注入支持简单类型和引用类型，Setter注入时在bean实例创建完成后执行的。

案例：
Address.java

public class Address {private String address;public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic String toString() {return "Address{" +"address='" + address + '\'' +'}';}
}

Student.java

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 Properties info;private String wife;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 List<String> getHobbys() {return hobbys;}public void setBooks(String[] books) {this.books = books;}public Map<String, String> getCard() {return card;}public void setCard(Map<String, String> card) {this.card = card;}public Properties getInfo() {return info;}public void setGames(Set<String> games) {this.games = games;}public Set<String> getGames() {return games;}public void setHobbys(List<String> hobbys) {this.hobbys = hobbys;}public String[] getBooks() {return books;}public void setInfo(Properties info) {this.info = info;}public String getWife() {return wife;}public void setWife(String wife) {this.wife = wife;}@Overridepublic String toString() {return "Student{" +"name='" + name + '\'' +", address=" + address.toString() +", books=" + Arrays.toString(books) +", hobbys=" + hobbys +", card=" + card +", games=" + games +", info=" + info +", wife='" + wife + '\'' +'}';}
}

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/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="address" class="com.hui.pojo.Address"><property name="address" value="背景"/></bean><!-- 依赖注入之set注入 --><bean id="student" class="com.hui.pojo.Student"><!--1. 普通值注入，value--><property name="name" value="李家辉"/><!--2. bean注入，ref--><property name="address" ref="address"/><!--3. 数组注入，array-value --><property name="books"><array><value>李</value><value>家</value><value>辉</value></array></property><!--list注入，list-value --><property name="hobbys"><list><value>语文</value><value>数学</value><value>英语</value></list></property><!--Map注入，map-entry-key-value --><property name="card"><map><entry key="身份证" value="123"/><entry key="银行卡" value="456"/></map></property><!--Set注入，set-value --><property name="games"><set><value>IOC</value><value>DI</value></set></property><!--null注入--><property name="wife"><null/></property><!----><property name="info"><props><prop key="学号">2019</prop><prop key="username">男</prop><prop key="password">123456</prop></props></property></bean>
</beans>

MyTest1.java

import com.hui.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;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.toString());/*** 结果分析：* Student{* name='李家辉',* address=Address{address='背景'},* books=[李, 家, 辉],* hobbys=[语文, 数学, 英语],* card={身份证=123, 银行卡=456},* games=[IOC, DI],* info={password=123456,* 学号=2019, username=男},* wife='null'* }* */}
}

运行结果：

3.c命名空间与p命名空间

p命名空间就是对应setter注入（property）；c命名空间就是对应构造方法注入（constructor-arg）。

案例
User.java

public class User {private String name;private int age;public User(){}public User(String name,int age){this.name=name;this.age=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;}@Overridepublic String toString() {return "User{" +"name='" + name + '\'' +", age=" + age +'}';}
}

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"xmlns:p="http://www.springframework.org/schema/p"xmlns:c="http://www.springframework.org/schema/c"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://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。p命名空间注入就是对应set注入的属性注入--><!--需要导入约束 xmlns:p="http://www.springframework.org/schema/p" --><bean id="user" class="com.hui.pojo.User" p:name="李家辉" p:age="22"/><!--c命名空间注入，对应所有的构造器注入，constructor-arg --><!--需要导入约束 xmlns:c="http://www.springframework.org/schema/c" --><bean id="user1" class="com.hui.pojo.User" c:name="李家毅" c:age="22"/>
</beans>

Test.java

public class Test {@org.junit.Testpublic void test(){ApplicationContext context=new ClassPathXmlApplicationContext("beans.xml");User user1=context.getBean("user1",User.class);User user=context.getBean("user",User.class);System.out.println(user1+"\n"+user);}
}

运行结果：