Spring 表達式語言(簡稱SpEL)：是一個支持運行時查詢和操作對象圖的強大的表達式語言。

語法類似于 EL：SpEL 使用 #{...} 作為定界符 , 所有在大括號中的字符都將被認為是 SpEL , SpEL 為 bean 的屬性進行動態賦值提供了便利。

通過 SpEL 可以實現：

通過 bean 的 id 對 bean 進行引用。
調用方式以及引用對象中的屬性。
計算表達式的值
正則表達式的匹配。

<?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="#{'瑪莎拉蒂'}"></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='#{"華崽兒"}'></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 ? '金領' : '白領'}"></property>
        <property name="address" value="#{address.province + '省' + address.city + '市' + address.area + '區'}"/>
    </bean>

    <bean id="address" class="com.itdjx.spring.spel.Address">
        <property name="province" value="#{'遼寧'}"/>
        <property name="city" value="#{'大連'}"/>
        <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;


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 + '\'' +
                '}';
    }
}

package com.itdjx.spring.spel;

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


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);

    }
}

控制臺輸出：

Person{name='華崽兒', age=25, marriage=false, car=Car{brand='瑪莎拉蒂', price=32000.78, perimeter='238.13273272948624'}, socialStatus='金領', address='遼寧省大連市沙河口區'}

SpEL 字面量：

整數：#{8}
小數：#{8.8}
科學計數法：#{1e4}
String：可以使用單引號或者雙引號作為字符串的定界符號。
Boolean：#{true}
SpEL引用bean , 屬性和方法：

引用其他對象:#{car}
引用其他對象的屬性：#{car.brand}
調用其它方法 , 還可以鏈式操作：#{car.toString()}
調用靜態方法靜態屬性：#{T(java.lang.Math).PI}
SpEL支持的運算符號：

算術運算符：+，-，*，/，%，^(加號還可以用作字符串連接)
比較運算符：< , > , == , >= , <= , lt , gt , eg , le , ge
邏輯運算符：and , or , not , |
if-else 運算符(類似三目運算符)：？:(temary), ?:(Elvis)
正則表達式：#{admin.email matches '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}'}