Spring依赖注入

依赖注入

构造器注入

前面有一篇文章写过，还有大神的依赖注入理解 https://blog.youkuaiyun.com/weixin_44424328/article/details/116656937

Set方式注入

• 依赖注入：使用set注入！
  • 依赖 ：bean对象的创建依赖于容器！
  • 注入 ：bean对象中的属性由容器来注入！

1. 搭建环境

• 复杂类型（省略get set 构造 tostring 下同）

public class Address {
    private String address;
}

• 整合类

public class Person {
    private String name;
    private Address address;
    private String[] books;
    private List<String> list;
    private Map<String,String> map;
    private Set<String> set;
    private Properties info;
    private String wife;
    private boolean flag;
    private List<Map<String,String>> mapList;
}

• sping配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="address" class="com.yxx.pojo.Address">
        <property name="address" value="四川"/>
    </bean>


    <bean id="person" class="com.yxx.pojo.Person">
        <!--简单类型使用value -->
        <property name="name" value="小明"/>

        <!-- 复杂类型使用引用 ref-->
        <property name="address" ref="address"/>

        <!-- 数组类型使用 array-->
        <property name="books">
            <array>
                <value>三国</value>
                <value>春秋</value>
                <value>论语</value>
            </array>
        </property>

        <!--list类型 -->
        <property name="list">
            <list>
                <value>c</value>
                <value>c++</value>
                <value>java</value>
            </list>
        </property>

        <!--map类型 -->
        <property name="map">
            <map>
                <entry key="川A" value="成都"/>
                <entry key="川B" value="绵阳"/>
                <entry key="川C" value="自贡"/>
            </map>
        </property>

        <!-- set类型-->
        <property name="set">
            <set>
                <value>LOL</value>
                <value>CF</value>
                <value>CS</value>
            </set>
        </property>

        <!-- Properties类型-->
        <property name="info">
            <props>
                <prop key="学9">603</prop>
                <prop key="学8">603</prop>
                <prop key="学7">603</prop>
            </props>
        </property>

        <!--属性赋null -->
        <property name="wife">
            <null/>
        </property>

        <property name="flag" value="true"/>

        <!--list map混合类型 标签套用即可 -->
        <property name="mapList">
            <list>
                <map>
                    <entry key="川D" value="攀枝花"/>
                    <entry key="川E" value="泸州"/>
                    <entry key="川F" value="德阳"/>
                </map>
            </list>
        </property>
    </bean>
</beans>

• 测试

@Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("ApplicationContent.xml");
        Person person = (Person) context.getBean("person");

        System.out.println(person);
        /*
        Person{name='小明',
         address=Address{address='四川'},
         books=[三国, 春秋, 论语],
         list=[c, c++, java],
         map={川A=成都, 川B=绵阳, 川C=自贡},
         set=[LOL, CF, CS],
         info={学8=603, 学7=603, 学9=603},
         wife='null',
         flag=true,
         mapList=[{川D=攀枝花, 川E=泸州, 川F=德阳}]}
         */
    }

拓展

采用c命名空间和p命名空间

• c命名空间就是使用的构造方法 与原来在bean中配置的constructor-arg类似

<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">

    <bean id="beanTwo" class="x.y.ThingTwo"/>
    <bean id="beanThree" class="x.y.ThingThree"/>

    <!-- traditional declaration with optional argument names -->
    <bean id="beanOne" class="x.y.ThingOne">
        <constructor-arg name="thingTwo" ref="beanTwo"/>
        <constructor-arg name="thingThree" ref="beanThree"/>
        <constructor-arg name="email" value="something@somewhere.com"/>
    </bean>

    <!-- c-namespace declaration with argument names -->
    <bean id="beanOne" class="x.y.ThingOne" c:thingTwo-ref="beanTwo"
        c:thingThree-ref="beanThree" c:email="something@somewhere.com"/>

</beans>

• p命名空间就是属性配置

<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">

    <bean name="classic" class="com.example.ExampleBean">
        <property name="email" value="someone@somewhere.com"/>
    </bean>

    <bean name="p-namespace" class="com.example.ExampleBean"
        p:email="someone@somewhere.com"/>
</beans>

注意：使用这两种方法需要注意的点，使用时需要导入他们各自的命名空间

c: xmlns:c=“http://www.springframework.org/schema/c”

p: xmlns:p=“http://www.springframework.org/schema/p”