构造方法注入和set方法注入

set方法注入

<?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">
    <!--id:用于从spring容器获得实例时使用-->
    <!--class:需要创建实例化的全限定名-->
    <!--property:类中的成员-->
    <!--scope是bean的作用域-->
    <!--scope属性有singleton单例模式,prototype多例模式-->
    <!--默认是单例模式-->
    <!--init-method初始化时调用该方法,destroy-method结束时调用该方法-->
    <bean id="messageService" init-method="init" destroy-method="destroy" class="com.spring.MessageService" scope="singleton">
        <!--name:成员的名称-->
        <!--value:对应属性的值-->
        <property name="message" value="hello spring"/>
    </bean>
</beans>

这是set方法注入

构造方法注入

对象信息

package com.spring;
public class MessageService {
    private String message;
    MessageService(String message) {
        this.message = message;
    }
    public void init() {
        System.out.println("init...");
    }
    public void destroy() {
        System.out.println("destroy");
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

这时候使用构造方法注入

<?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">
    <!--构造方法注入-->
    <bean id="messageService" class="com.spring.MessageService">
        <!--name是带参数构造方法的参数名称-->
        <constructor-arg name="message" value="Hello Spring"></constructor-arg>
    </bean>
</beans>

构造方法注入应当使用标签
set方法使用

当在Bean增加字段

package com.spring;
public class MessageService {
    private String message;
    private String name;
    MessageService(String message, String name) {
        this.message = message;
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void init() {
        System.out.println("init...");
    }
    public void destroy() {
        System.out.println("destroy");
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

这时候配置中有三种方式

<?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">
    <!--构造方法注入-->
   <bean id="messageService" class="com.spring.MessageService">
        <!--name是带参数构造方法的参数名称-->
        <constructor-arg index="0" value="Hello Spring"></constructor-arg>
        <constructor-arg index="1" value="Spring"></constructor-arg>
        -------------------------------------------------------------------
        <constructor-arg type="java.lang.String" value="Hello Spring"></constructor-arg>
        <constructor-arg type="java.lang.String" value="Spring"></constructor-arg>
        --------------------------------------------------------------------
        <constructor-arg name="message" value="Hello Spring"></constructor-arg>
        <constructor-arg name="name" value="Spring"></constructor-arg>
    </bean>
</beans>

以上三种方式用 - 隔开