Spring SpEL表達式語言
一、說在前面
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。語法類似於 EL:SpEL 使用 #{…} 作爲定界符,所有在大框號中的字符都將被認爲是 SpEL。SpEL 爲 bean 的屬性進行動態賦值提供了便利。
通過 SpEL 可以實現:
(1)通過 bean 的 id 對 bean 進行引用;
(2)調用方法以及引用對象中的屬性;
(3)計算表達式的值;
(4)正則表達式的匹配。
二、舉例說明
1、Address、Car和Person類
Address類:
package com.at.beans.spel;
public class Address {
private String city;
private String street;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
@Override
public String toString() {
return "Address [city=" + city + ", street=" + street + "]";
}
}
Car類
package com.at.beans.spel;
public class Car {
private String brand;
private double price;
//輪胎周長
private double ltzhouchang;
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 getLtzhouchang() {
return ltzhouchang;
}
public void setLtzhouchang(double ltzhouchang) {
this.ltzhouchang = ltzhouchang;
}
@Override
public String toString() {
return "Car [brand=" + brand + ", price=" + price + ", ltzhouchang="
+ ltzhouchang + "]";
}
}
Person類
package com.at.beans.spel;
public class Person {
private String name;
private Car car;
//引用address bean的city屬性
private String city;
//根據car的price屬性來確定info:car的price>400000爲金領,否則爲白領
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 + "]";
}
}
<?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="address" class="com.at.beans.spel.Address">
<!-- 使用SpEL爲屬性賦一個字面值 -->
<property name="city" value="#{'BeiJing'}"></property>
<property name="street" value="huoying"></property>
</bean>
<bean id="car" class="com.at.beans.spel.Car">
<property name="brand" value="Audi"></property>
<property name="price" value="300000"></property>
<!-- 使用SpEL引用類的靜態屬性 -->
<property name="ltzhouchang" value="#{T(java.lang.Math).PI * 50}"></property>
</bean>
<bean id="person" class="com.at.beans.spel.Person">
<!-- 使用SpEL來應用其他的bean -->
<property name="car" value="#{car}"></property>
<!-- 使用SpEL來應用其他的bean的屬性 -->
<property name="city" value="#{address.city}"></property>
<!-- 使用SpEL中使用運算符 -->
<property name="info" value="#{car.price > 400000 ? '金領':'白領'}"></property>
<property name="name" value="luoyepiaoxue2014"></property>
</bean>
</beans>
package com.at.beans.spel;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class TestSpel {
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);
}
}
五月 24, 2017 9:40:45 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@427a39ea: startup date [Wed May 24 21:40:45 CST 2017]; root of context hierarchy
五月 24, 2017 9:40:45 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [beans-spel.xml]
Address [city=BeiJing, street=huoying]
Car [brand=Audi, price=300000.0, ltzhouchang=157.07963267948966]
Person [name=luoyepiaoxue2014, car=Car [brand=Audi, price=300000.0, ltzhouchang=157.07963267948966], city=BeiJing, info=白領]
By luoyepiaoxue2014
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