Spring学习-- SpEL表达式

Spring 表达式语言(简称SpEL)：是一个支持运行时查询和操作对象图的强大的表达式语言。

语法类似于 EL：SpEL 使用 #{...} 作为定界符 , 所有在大括号中的字符都将被认为是 SpEL , SpEL 为 bean 的属性进行动态赋值提供了便利。

通过 SpEL 可以实现：

• 通过 bean 的 id 对 bean 进行引用。
• 调用方式以及引用对象中的属性。
• 计算表达式的值
• 正则表达式的匹配。

 <?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="car" class="com.itdjx.spring.spel.Car">
         <property name="brand" value="#{'玛莎拉蒂'}"></property>
         <property name="price" value="#{32000.78}"></property>
         <property name="perimeter" value="#{T(java.lang.Math).PI * 75.8f}"></property>
     </bean>

     <bean id="person" class="com.itdjx.spring.spel.Person">
         <property name='name' value='#{"华崽儿"}'></property>
         <property name="age" value="#{25}"></property>
         <property name="marriage" value="#{car.price > 400000 and age > 30}"></property>
         <property name="car" value="#{car}"></property>
         <property name="socialStatus" value="#{car.price > 30000 ? '金领' : '白领'}"></property>
         <property name="address" value="#{address.province + '省' + address.city + '市' + address.area + '区'}"/>
     </bean>

     <bean id="address" class="com.itdjx.spring.spel.Address">
         <property name="province" value="#{'辽宁'}"/>
         <property name="city" value="#{'大连'}"/>
         <property name="area" value="#{'沙河口'}"/>
     </bean>

 </beans>

 package com.itdjx.spring.spel;

 /**
  * @author Wáng Chéng Dá
  * @create 2017-03-02 13:26
  */
 public class Car {

     private String brand;

     private double price;

     private String perimeter;

     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 String getPerimeter() {
         return perimeter;
     }

     public void setPerimeter(String perimeter) {
         this.perimeter = perimeter;
     }

     @Override
     public String toString() {
         return "Car{" +
                 "brand='" + brand + '\'' +
                 ", price=" + price +
                 ", perimeter='" + perimeter + '\'' +
                 '}';
     }
 }

 package com.itdjx.spring.spel;

 /**
  * @author Wáng Chéng Dá
  * @create 2017-03-02 13:48
  */
 public class Address {

     private String province;

     private String city;

     private String area;

     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;
     }

     public String getArea() {
         return area;
     }

     public void setArea(String area) {
         this.area = area;
     }

     @Override
     public String toString() {
         return "Address{" +
                 "province='" + province + '\'' +
                 ", city='" + city + '\'' +
                 ", area='" + area + '\'' +
                 '}';
     }
 }

 package com.itdjx.spring.spel;

 /**
  * @author Wáng Chéng Dá
  * @create 2017-03-02 13:27
  */
 public class Person {

     private String name;

     private int age;

     private boolean marriage;

     private Car car;

     private String socialStatus;

     private String address;

     public String getName() {
         return name;
     }

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

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public boolean isMarriage() {
         return marriage;
     }

     public void setMarriage(boolean marriage) {
         this.marriage = marriage;
     }

     public Car getCar() {
         return car;
     }

     public void setCar(Car car) {
         this.car = car;
     }

     public String getSocialStatus() {
         return socialStatus;
     }

     public void setSocialStatus(String socialStatus) {
         this.socialStatus = socialStatus;
     }

     public String getAddress() {
         return address;
     }

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

     @Override
     public String toString() {
         return "Person{" +
                 "name='" + name + '\'' +
                 ", age=" + age +
                 ", marriage=" + marriage +
                 ", car=" + car +
                 ", socialStatus='" + socialStatus + '\'' +
                 ", address='" + address + '\'' +
                 '}';
     }
 }

package com.itdjx.spring.spel;

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

/**
 * @author Wáng Chéng Dá
 * @create 2017-03-02 13:42
 */
public class Main {

    public static void main(String[] args) {

        ApplicationContext app = new ClassPathXmlApplicationContext("spel-beans.xml");
        Person person = (Person) app.getBean("person");
        System.out.println(person);

    }
}

控制台输出：

Person{name='华崽儿', age=25, marriage=false, car=Car{brand='玛莎拉蒂', price=32000.78, perimeter='238.13273272948624'}, socialStatus='金领', address='辽宁省大连市沙河口区'}

 SpEL 字面量：

• 整数：#{8}
• 小数：#{8.8}
• 科学计数法：#{1e4}
• String：可以使用单引号或者双引号作为字符串的定界符号。
• Boolean：#{true}

SpEL引用bean , 属性和方法：

• 引用其他对象:#{car}
• 引用其他对象的属性：#{car.brand}
• 调用其它方法 , 还可以链式操作：#{car.toString()}
• 调用静态方法静态属性：#{T(java.lang.Math).PI}

 SpEL支持的运算符号：

• 算术运算符：+，-，*，/，%，^(加号还可以用作字符串连接)
• 比较运算符：< , > , == , >= , <= , lt , gt , eg , le , ge
• 逻辑运算符：and , or , not , |
• if-else 运算符(类似三目运算符)：？:(temary), ?:(Elvis)
• 正则表达式：#{admin.email matches '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4}'}