依赖注入(DI)

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!

注入方式

构造器注入

Set方式注入【重点】

**必须要有getter和setter方法

• pojo.java

@Data
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;
}

• 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.spring.pojo.Address">
        <property name="address" value="北京"/>
    </bean>

    <bean id="student" class="com.spring.pojo.Student" >
    <!--第一种，普通值注入，value-->
    <property name="name" value="Kitty Guy"/>
        <!--第二种，Bean注入，ref-->
    <property name="address" ref="address" />
        <!--数组-->
    <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>
        <!--List-->
    <property name="hobbys">
        <list>
            <value>听歌</value>
            <value>敲代码</value>
            <value>看电影</value>
        </list>
    </property>
        <!--Map-->
        <property name="card">
            <map>
                <entry key="身份证" value="111111222222223333"/>
                <entry key="银行卡" value="132123131231231312中"/>
            </map>
        </property>
        <!--Set-->
        <property name="games">
            <set>
                <value>LoL</value>
                <value>CS:Go</value>
                <value>Apex</value>
            </set>
        </property>
        <!--null-->
        <property name="wife">
            <null/>
        </property>
        <!--Properties-->
        <property name="info">
            <props>
                <prop key="driver">20190525</prop>
                <prop key="ur1">男</prop>
                <prop key="username">root</prop>
                <prop key="password">123456</prop>
            </props>
        </property>
    </bean>
</beans>

拓展方式注入

• p命名空间(property) 定义命名空间

 xmlns:p="http://www.springframework.org/schema/p"

• c命名空间(constructor) 定义命名空间,使用时需要类含有有参构造器

xmlns:c="http://www.springframework.org/schema/c"

• 样例 pojo

@Data
public class People {
    int age;
    String name;

    public People(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public People() {
    }
}

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">
    <bean id="people1" class="com.spring.pojo.People" p:age="18" p:name="老王"/>
    
    <bean id="people2" class="com.spring.pojo.People" c:age="48" c:name="老李"/>
</beans>

test

public class Mytest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("namespace.xml");
        People people1=context.getBean("people1",People.class);
        People people2=context.getBean("people2",People.class);
        System.out.println(people1);
        System.out.println(people2);
        //System.out.println(exampleBean1==exampleBean);

    }
}

Note

p 命名空间不如标准 XML 格式灵活。例如，用于声明属性引用的格式与以Ref结尾的属性发生冲突，而标准 XML 格式则没有。我们建议您谨慎选择方法，并与团队成员进行交流，以免产生同时使用这三种方法的 XML 文档。

Bean的作用域