Spring的依赖注入及三种配置方式（依赖注入的两种形式）

依赖注入的两种形式

1.1构造方法注入

LowerAction.class

public class LowerAction implements Action {
    private String prefix;
    private String message;

    public  LowerAction(){}

    public  LowerAction(String prefix, String message){
        this.prefix = prefix;
        this.message = message;
    }
    public String getPrefix() {
        return prefix;
    }
    public String getMessage() {
        return message;
    }
    public void setPrefix(String string) {
        prefix = string;
    }
    public void setMessage(String string) {
        message = string;
    }
    public void execute(String str) {
        System.out.println((getPrefix() + ", " + getMessage() + ", " + str).toLowerCase());
    }
}

ApplicationContext.xml中的TheAction2的Bean

    <bean id="TheAction2" class="com.example.service.LowerAction">
        <constructor-arg index="0">
            <value>Hi</value>
        </constructor-arg>
        <constructor-arg index="1">
            <value>Good Afternoon</value>
        </constructor-arg>
    </bean>

测试函数

    @Test
    public void test5() {
        String XML = "file:src/applicationContext.xml";
        ApplicationContext ctx = new ClassPathXmlApplicationContext(XML);

        LowerAction lowerAction=(LowerAction) ctx.getBean("TheAction2");
        System.out.println(lowerAction.getPrefix());
        System.out.println(lowerAction.getMessage());

    }

测试结果

实验中想到的问题：构造注入只能通过index索引匹配吗？
还有类型匹配

<bean id="TheAction4" class="com.example.service.LowerAction">
        <constructor-arg type="java.lang.String">
            <value>Hi</value>
        </constructor-arg>
        <constructor-arg type="java.lang.String">
            <value>Wushuohan</value>
        </constructor-arg>
    </bean>

以及参数名传值

<bean id="TheAction6" class="com.example.service.LowerAction">
        <constructor-arg name="prefix" value="Hi">
        </constructor-arg>
        <constructor-arg type="message" value="Wushuohan">
        </constructor-arg>
    </bean>

测试结果如下

测试结果

Setter()方法注入

ApplicationContext.xml中的TheAction1的Bean

<bean id="TheAction1" class="com.example.service.LowerAction">
        <property name="prefix">
            <value>Hi</value>
        </property>
        <property name="message">
            <value>Good Morning</value>
        </property>
    </bean>

测试函数

    @Test
    public void test4() {
        String XML = "file:src/applicationContext.xml";
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext(XML);
        LowerAction lowerAction=(LowerAction) ctx.getBean("TheAction1");
        System.out.println(lowerAction.getPrefix());
        System.out.println(lowerAction.getMessage());
    }

测试结果如下

测试结果

实验中想到的问题：Setter()注入能不能没有构造函数？
注释掉LowerAction的构造函数

public class LowerAction implements Action {
    private String prefix;
    private String message;

    public void execute(String str) {
        System.out.println((getPrefix() + ", " + getMessage() + ", " + str).toLowerCase());
    }
}

运行后报错