Spring基于XML的DI-使用SPEL注入

Spring基于XML的DI-使用SPEL注入

SpEL，Spring Expression Language，即Spring EL表达式语言。在Spring配置文件中为Bean的属性注入值时，可直接使用SpEL表达式计算的结果。SpEl表达式一#开头，后跟一对大括号​​<bean id="hello" value="#{……}">​​​

其配置方法在​​spring-framework-4.2.1.RELEASE-dist\spring-framework-4.2.1.RELEASE\docs\spring-framework-reference\html.index​​​中有详细讲述，Ctrl+F​​SpEL​​​

举个栗子

Student.java

package com.hk.spring.di09;

public class Student {

    private String name;
    private int age;
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + "]";
    }


}

Person.java

package com.hk.spring.di09;

public class Person {

    private String personName;
    public String getPersonName() {
        return personName;
    }
    public int getPersonAge() {
        return personAge;
    }
    private int personAge;
    public void setPersonName(String personName) {
        this.personName = personName;
    }
    public void setPersonAge(int personAge) {
        this.personAge = personAge;
    }
    /**
     *  大于25就返回25
     * @param personAge
     * @return
     */
    public int countAge(int personAge){
        return personAge > 25 ? 25 : personAge;
    }
    @Override
    public String toString() {
        return "Person [personName=" + personName + ", personAge=" + personAge
                + "]";
    }
}

配置（applicationContext.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">

    <!-- personAge年龄为50以内随机数 -->
    <bean id="person" class="com.hk.spring.di09.Person">
        <property name="personName" value="李四"/>
        <property name="personAge" value="#{T(java.lang.Math).random()*50}"/>
    </bean>
    <!-- myStudent的属性与 person值相同-->
    <bean id="myStudent" class="com.hk.spring.di09.Student" autowire="byType">
        <!-- person.personName底层调用的是bean的Get方法，bean内必须包含属性的get方法 -->
        <property name="name" value="#{person.personName}"/>
        <!-- 调用bean的方法 -->
        <property name="age" value="#{person.countAge(person.personAge)}"/>
    </bean>
</beans>

MyTest.java

package com.hk.spring.di09;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Mytest {
    @Test
    public void test1(){
        String resource = "com/hk/spring/di09/applicationContext.xml";
        ApplicationContext ac = new ClassPathXmlApplicationContext(resource);
        Student stu = (Student) ac.getBean("myStudent");
        Person person = (Person) ac.getBean("person");
        System.out.println(stu+"\n"+person);

    }
}

结果

Student [name=李四, age=25]
Person [personName=李四, personAge=30]