spring学习笔记（8）——SpEL

什么是SpEL

spel就是spring的表达式语言，看下图（该图来自尚硅谷）

SpEL很重要的一个功能就是能够实现 动态赋值

最简单的用法

以上的用法其实没有什么意义，并不能体现出SpEL的强大

SpEL使用

先写三个实体类

package com.zj.spel;public class Address {    private String province;    private String city;    public String getProvince() {        return province;    }    public void setProvince(String province) {        this.province = province;    }    public String getCity() {        return city;    }    public void setCity(String city) {        this.city = city;    }    @Override    public String toString() {        return "Address [province=" + province + ", city=" + city + "]";    }}

package com.zj.spel;public class Car {    private String brand;    private double price;    private double tyrePerimeter;//轮胎周长    public String getBrand() {        return brand;    }    public void setBrand(String brand) {        this.brand = brand;    }    public double getPrice() {        return price;    }    public void setPrice(double price) {        this.price = price;    }    public double getTyrePerimeter() {        return tyrePerimeter;    }    public void setTyrePerimeter(double tyrePerimeter) {        this.tyrePerimeter = tyrePerimeter;    }    @Override    public String toString() {        return "Car [brand=" + brand + ", price=" + price + ", tyrePerimeter="                + tyrePerimeter + "]";    }}

package com.zj.spel;public class Person {    private String name;    private Car car;    //引用Address的city属性    private String city;    //根据car的价格：价格>300000，有钱人；价格<300000：普通人    private String info;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Car getCar() {        return car;    }    public void setCar(Car car) {        this.car = car;    }    public String getCity() {        return city;    }    public void setCity(String city) {        this.city = city;    }    public String getInfo() {        return info;    }    public void setInfo(String info) {        this.info = info;    }    @Override    public String toString() {        return "Person [name=" + name + ", car=" + car + ", city=" + city                + ", info=" + info + "]";    }}

配置文件中使用spel

<?xml version="1.0" encoding="UTF-8"?><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"    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-4.0.xsd">    <!-- 使用spel赋字面值 -->    <bean id="address" class="com.zj.spel.Address">        <property name="province" value="#{'福建'}"></property>        <property name="city" value="#{'福州'}"></property>    </bean>    <!-- 使用spel引用类的静态属性 -->    <bean id="car" class="com.zj.spel.Car">        <property name="brand" value="bmw"></property>        <property name="price" value="350000"></property>        <!-- 引用Math类的静态属性PI -->        <property name="tyrePerimeter" value="#{T(java.lang.Math).PI * 80}"></property>    </bean>    <bean id="person" class="com.zj.spel.Person">        <property name="name" value="tom"></property>        <!-- 使用spel引用其他的bean -->        <property name="car" value="#{car}"></property>        <!-- 使用spel引用其他bean的属性 -->        <property name="city" value="#{address.city}"></property>        <!-- 使用spel -->        <property name="info" value="#{car.price > 300000 ? '有钱人' : '普通人'}"></property>    </bean></beans>

写一个测试方法

    public static void main(String[] args) {        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-spel.xml");        Address address = (Address) ctx.getBean("address");        System.out.println(address);        Car car = (Car) ctx.getBean("car");        System.out.println(car);        Person person = (Person) ctx.getBean("person");        System.out.println(person);    }

结果

用法总结

截图来自尚硅谷