SpEL表达式

素颜马尾好姑娘i 2022-02-20 19:47 178阅读 0赞

**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。

### **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 '\[a-zA-Z0-9.\_%+-\]+@\[a-zA-Z0-9.-\]+\\\\.\[a-zA-Z\]\{实例

### **实例：** ###

<?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>

**对应的JavaBean**

package com.itdjx.spring.spel;
    
    
    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;
    
    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;
    
    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 + '\'' +'}';
        }
    }

**控制台输出：**

<table> 
 <tbody> 
  <tr> 
   <td>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'}</td> 
  </tr> 
 </tbody> 
</table>