spring SpEL

概要：

Spring表达式语言：SpEL

• Spring表达式语言（简称SpEL）：是一个支持执行时查询和操作对象图的强大的表达式语言
• 语言类似于EL：SpEL使用＃{…} 作为定界符，全部在大括号里的字符都将被觉得是SpEL
• SpEL为bean的属性进行动态赋值提供了便利
• 通过SpEL能够实现：
  • 通过bean的id对bean进行引用
  • 调用方法以及引用对象中的属性
  • 计算表达式的值
  • 正則表達式的匹配 

实例代码具体解释

文件夹结构（用到的包）

Address.java

package com.coslay.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.java

package com.coslay.beans.spel;

public class Car {
	private String brand;
	private double price;
	// 轮胎的周长
	private double tyrePerimeter;

	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 Car() {
		System.out.println("Car's Constructor...");
	}

	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 + "]";
	}

}

Person.java

package com.coslay.beans.spel;

public class Person {
	private String name;
	private Car car;
	// 引用address bean的city属性
	private String city;
	// 依据car的price确定info：car的price》＝300000:金额
	// 否则为：白领
	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 + "]";
	}

}

Main.java

package com.coslay.beans.spel;

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

public class Main {
	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);
	}
}

beans-spel.xml

<?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.coslay.beans.spel.Address">
		<!-- 使用spel为属性赋一个字面值 -->
		<property name="city" value="#{'beijint'}"></property>
		<property name="street" value="WuDaoKou"></property>
	</bean> 
	
	<bean id="car" class="com.coslay.beans.spel.Car">
		<property name="brand" value="Audi"></property>
		<property name="price" value="5000000"></property>
		<!-- 使用SpEL引用类的静态属性 -->
		<property name="tyrePerimeter" value="#{T(java.lang.Math).PI * 80}"></property>
	</bean>
	
	<bean id="person" class="com.coslay.beans.spel.Person">
		<!-- 使用 SpEL来引用其它的Bean -->
		<property name="car" value="#{car}"></property>
		<!-- 使用SpEL来引用其它的Bean的属性 -->
		<property name="city" value="#{address.city}"></property>
		<!-- SpEL中使用运算符 -->
		<property name="info" value="#{car.price > 300000 ? '金领' : '白领'}"></property>
		<property name="name" value="Tom"></property>
	</bean>
</beans>