Spring expression language (SpEL) allow developer uses expression to execute method and inject the method returned value into property, or so called “SpEL method invocation“.
Spring EL in Annotation
See how to do Spring EL method invocation with @Value annotation.
package com.mkyong.core;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component("customerBean")
public class Customer {
@Value("#{'mkyong'.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.mkyong.core;
import org.springframework.stereotype.Component;
@Component("priceBean")
public class Price {
public double getSpecialPrice() {
return new Double(99.99);
}
}
Output
Customer [name=MKYONG, amount=99.99]
Explanation
Call the ‘toUpperCase()‘ method on the string literal.
@Value("#{'mkyong'.toUpperCase()}")
private String name;
Call the ‘getSpecialPrice()‘ method on bean ‘priceBean‘.
@Value("#{priceBean.getSpecialPrice()}")
private double amount;
Spring EL in XML
This is the equivalent version in bean definition XML file.
<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.mkyong.core.Customer">
<property name="name" value="#{'mkyong'.toUpperCase()}" />
<property name="amount" value="#{priceBean.getSpecialPrice()}" />
</bean>
<bean id="priceBean" class="com.mkyong.core.Price" />
</beans>
Output
Customer [name=MKYONG, amount=99.99]
Download Source Code
Download It – Spring3-EL-Method-Invocation-Example.zip (6 KB)
Can we do like this ?
What if the method we are calling from SPEL throws an exception, how to handle that ?
I think that if you are calling a method from within your view that throws an exception then you are putting too much business logic there. This is probably something that should be handled by the model or controller.
How to send input to a bean for an output
can you give example on difference between @bean and @component. I got confused after studying your above tutorial. I mean in all the previous tuts you used @bean to create bean but in this example you used @component to create a bean.
Really very helpful tutorials.
Thanks a lot Sir.