Spring基于XML的DI-使用SPEL注入

傷城~ 2023-10-17 12:06 54阅读 0赞

### 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`         ![这里写图片描述][SouthEast] #####

### 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">
    
        
        <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>
        
        <bean id="myStudent" class="com.hk.spring.di09.Student" autowire="byType">
            
            <property name="name" value="#{person.personName}"/>
            
            <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]

[SouthEast]: https://img-blog.csdn.net/20170329172350465?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvbGVpc3VyZV9saWZl/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast