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/beans
       http://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;
    }

    @Override
    public 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;
    }

    @Override
    public 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/beans
       http://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;
    }

    @Override
    public 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/beans
       http://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.Test
    public 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：