17 Spring EL方法调用实例

Spring表达式语言(使用SpEL)允许开发人员使用表达式来执行方法和将返回值以注入的方式到属性，或叫作“使用SpEL方法调用”。

Spring EL在注解的形式

了解如何实现Spring EL方法调用与@Value注释。

package com.gp6.el.method;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("customerBean")
public class Customer {
    @Value("#{'gp6'.toUpperCase()}")
    private String name;

    @Value("#{priceBean.getSpecialPrice()}")
    private double amount;

    public String getName() {
        return name;
    }

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

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    @Override
    public String toString() {
        return "Customer [name=" + name + ", amount=" + amount + "]";
    }

}

package com.gp6.el.method;

import org.springframework.stereotype.Component;

@Component("priceBean")
public class Price {
    public double getSpecialPrice() {
        return new Double(199.09);
    }
}

配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan base-package="com.gp6.el.method" />

</beans>

测试文件

package com.gp6.el.method;

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

public class Test {

     public static void main( String[] args ) {
            
         ApplicationContext context = new ClassPathXmlApplicationContext(
                    "com/gp6/el/method/el_method.xml");

         Customer customer = (Customer) context.getBean("customerBean");
         System.out.println(customer);
    }
    
}

执行结果

Customer [name=GP6, amount=199.09]

使用xml文件达到相同效果

<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-3.0.xsd">
 
    <bean id="customerBean" class="com.gp6.el.method.Customer">
        <property name="name" value="#{'gp6'.toUpperCase()}" />
        <property name="amount" value="#{priceBean.getSpecialPrice()}" />
    </bean>
 
    <bean id="priceBean" class="com.gp6.el.method.Price" />
    
</beans>