Spring：SpEL表达式（了解）

一、什么是SpEL表达式

SpEL表达式语言是一种表达式语言，是一种可以与一个基于spring的应用程序中的运行时对象交互的东西，总得来说SpEL表达式是一种简化开发的表达式，通过使用表达式来简化开发，减少一些逻辑、配置的编写。
二、简单的配置代码实现
1、Address和Customer类

public class Address {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Address{" +
                "name='" + name + '\'' +
                '}';
    }
}

public class Customer {
    private String name;
    private String sex = "男";
    private double pi;
    private Address address;

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public double getPi() {
        return pi;
    }

    public void setPi(double pi) {
        this.pi = pi;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", pi=" + pi +
                '}';
    }


}

2、beans.xml配置文件内容

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd">

    

    

    <bean id="address" class="com.model.Address">
        <property name="name" value="中南民族大学">property>
    bean>
    

    <bean id="customer" class="com.model.Customer">
        <property name="name" value="#{'cjx'.toUpperCase()}">property>
        
        <property name="pi" value="#{T(java.lang.Math).PI}">property>
        
        <property name="address" value="#{address}">property>

    bean>
    
beans>

3、创建Lesson测试

public class Lesson3 {

    @Test
    public void test() throws Exception{

        /*
        * spel:spring表达式
        * */
        ApplicationContext context = new ClassPathXmlApplicationContext("beans3.xml");
        Customer customer = (Customer) context.getBean("customer");
        System.out.println(customer);
        System.out.println(customer.getAddress());
    }
}

4、测试运行结果