spring 依赖注入 DI

User

@ToString
@Getter
public class User {
    private Integer id;
    private String name;
    private Car car;
    private List<String> products;
    private Map<String, String> map;
    private List<Car> cars;
    //private Map<String, Car> mapCar;
    //private Map<String, List<Car>> mapListCar;

    public User(Integer id, String name, Car car) {
        System.out.println("user 有参构造");
        this.id = id;
        this.name = name;
        this.car = car;
    }

    public User() {
        System.out.println("user 无参构造");
    }

    public void setId(Integer id) {
        System.out.println("user setId");
        this.id = id;
    }

    public void setName(String name) {
        System.out.println("user setName");
        this.name = name;
    }

    public void setCar(Car car) {
        System.out.println("user setCar");
        this.car = car;
    }

    public void setProducts(List<String> products) {
        this.products = products;
    }

    public void setCars(List<Car> cars) {
        this.cars = cars;
    }

    public void setMap(Map<String, String> map) {
        this.map = map;
    }
}

1. 有参构造

applicationContext.xml

constructor-arg 标签五个属性
index：从0开始，对应构造函数中参数顺序
name：参数名字
value：赋值
ref：当属性是对象时，值为对应该类的bean id
type：可以不写，自动识别

<bean id="user" class="net.wanho.pojo.User">
    <constructor-arg name="id" value="11"/>
    <constructor-arg name="name" value="张三"/>
    <constructor-arg name="car" ref="car" type="net.wanho.pojo.Car"/>
</bean>

<bean id="car" class="net.wanho.pojo.Car">
    <constructor-arg name="id" value="1"/>
    <constructor-arg name="name" value="大G"/>
</bean>

测试

@Test
public void constructorArgs() {
    ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
    User user = ac.getBean("user", User.class);
    System.out.println(user);
}

user 有参构造
User(id=11, name=张三, car=Car{id=1, name='大G'})

2. 无参构造和set方法

applicationContext.xml

property 标签4个属性
name：setXXX方法 将set去掉，并且首字母小写 比如setId 写作id
value：给简单类型赋值
ref：给引用类型赋值，值为该类在spring容器中的bean id
type：可以不写，自动识别

<bean id="user" class="net.wanho.pojo.User">
     <!-- 简单类型 -->
    <property name="id" value="11"/>
    <property name="name" value="张三"/>
    <!-- 单个引用 指向外部 -->
    <property name="car" ref="car" />
    <!--
        简单类型集合 相同类型标签可以通用
        单个元素：list set array
        键值对：map props
    -->
    <property name="products">
        <list>
            <value>苹果</value>
            <value>华为</value>
            <value>三星</value>
        </list>
    </property>
    <!-- Map<String, String> -->
    <property name="map">
        <map>
            <entry key="1" value="a"/>
            <entry key="2" value="b"/>
            <entry>
                <key>
                    <value>3</value>
                </key>
                <value>c</value>
            </entry>
        </map>
    </property>
    <!-- 
        泛型为引用的集合
        ref 引用外部创建好的bean
        bean 新建一个bean
    -->
    <property name="cars">
        <list>
            <ref bean="car"/>
            <ref bean="car"/>
            <bean class="net.wanho.pojo.Car">
                <property name="id" value="3"/>
                <property name="name" value="奥迪"/>
            </bean>
        </list>
    </property>
</bean>

<bean id="car" class="net.wanho.pojo.Car">
    <property name="id" value="2"/>
    <property name="name" value="大鳄"/>
</bean>

测试

@Test
public void constructorArgs() {
    ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
    User user = ac.getBean("user", User.class);
    System.out.println(user);
}

user 无参构造
car 无参构造
car setId
car setName
car 无参构造
car setId
car setName
user setId
user setName
user setCar
User(id=11, name=张三, car=Car{id=2, name='大鳄'}, products=[苹果, 华为, 三星], map={1=a, 2=b, 3=c}, cars=[Car{id=2, name='大鳄'}, Car{id=2, name='大鳄'}, Car{id=3, name='奥迪'}])

3. p名称空间

applicationContext.xml

p名称空间 p:属性名="值"
本质上还是使用property标签 set方法注入
使注入对象类型，p:属性名-ref="id"
p名称空间不建议使用，就使用property标签

<bean id="employee1" class="net.wanho.pojo.Employee" p:id="1002" p:name="李四" p:menu-ref="menu"/>

<bean id="menu" class="net.wanho.pojo.Menu">
    <property name="id" value="112"/>
    <property name="name" value="职位管理"/>
</bean>