SpEL: Wiring bean

Spring 3 provides powerful Expression Language which can be used to wire beans. Lets take an example to demonstrate how SpEL is used to wire bean.

Product.java: The Product class contains property named part which is of Part type.

package spel.wiringbean;

import java.util.*;
import spel.wiringbean.Part;

public class Product
{
private Part part;

public void setPart(Part part) {
this.part = part;
}
public Part getPart() {
return part;
}
}

Part.java: This class contains the name of the part and will be used in configuration file to provide this name to the part property of Product bean.

package spel.wiringbean;

import java.util.*;

public class Part
{
private String name;

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

spring-beans.xml: Using Spring expression language the property part of Product bean is wired with the part bean with the text #{part}.

<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-2.5.xsd">

<bean id="product" class="spel.wiringbean.Product">
<property name="part" value="#{part}"/>
</bean>
<bean id="part" class="spel.wiringbean.Part">
<property name="name" value="Monitor"/>
</bean>
</beans>

AppMain.java: This class loads the context configuration file spring-beans-list.xml from the class path.

package spel.wiringbean;

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

import spel.wiringbean.Product;
import spel.wiringbean.Part;
import java.util.*;

public class AppMain{
public static void main( String[] args ){
ApplicationContext appContext = new ClassPathXmlApplicationContext(new String[] {"spel\\wiringbean\\spring-beans-list.xml"});
Product product = (Product)appContext.getBean("product");

System.out.println(product.getPart().getName());
}
}

The output of the above program will be as below:

Monitor

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