Spring Dependency Injection With Set Collection Property

Let us see few points, if we have Set property in our program

• If in our spring bean has a property of type Set then in the spring config xml file, we need to use <set> element to inform the Spring IOC container regarding that Set property
• In spring config xml, we can use <value /> and <ref /> tags as sub elements of <set> tag
• While configuring <set> in xml file it doesnt allow duplicate values, because Set collection is a unique collection
• In spring framework if one bean is collaborating[depends on] with other bean class then  spring ioc container first creates collaborator bean object after only dependent bean object

Example

public class SampleBean
{
   private Set studentsData;
   private TestBean tb;

   public void setStudentsData(Set studentsData)
   {
      this.studentsData = studentsData;
   }

   public void setTb(TestBean tb)
   {
      this.tb = tb;
   }     

   public void m1()
   {
       // Some Logic
   }

}

Our XML

<beans>

<bean id="id1" class="SampleBean">
      <property name="studentsData">
            <set>
               <value>sun</value>
               <value>Oracle</value>
               <value>java4s</value>
               <ref bean="id2">
            </set>
      </property>
</bean>

<bean id="id2" class="TestBean"/>

</beans>

Explanation:

Now in our client when we call getBean(“id1”) then spring framework executes, following code internally [ not be visible 🙂 ]

TestBean tb = new TestBean();
Set s = new HastSet();
s.add("sun");
s.add("oracle");
s.add("java4s");
SampleBean ob =new SampleBean();
ob.setStudentsData(s);

First spring ioc creates TestBean class object as SampleBean depends on TestBean, then creates the Set object and will add the data into the set object and finally our SampleBean object will be created and set object will be injected.

Actually nothing mates,  just like primitive value injections, just we used Collections here nothing more than that 🙂 , download this example and test.

Complete Example On Spring Setter Injection With Set Collection Property

files will be used..

• WelcomeBean.java
• ClientLogic.java
• spconfig.xml

Directory structure:

WelcomeBean.java

package java4s;
import java.util.Set;
public class WelcomeBean {

       private Set studentsData;      
    

    public void setStudentsData(Set studentsData) {
        this.studentsData = studentsData;
    }

    public void show()
       {
           System.out.println(studentsData);
       }

}

spconfig.xml

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
"http://www.springframework.org/dtd/spring-beans-2.0.dtd">

<beans>
  <bean id="id1" class="java4s.WelcomeBean">
 
    <property name="studentsData" >
      <set>
         <value>java4s</value>
         <value>sun</value>
         <value>oracle</value>
         <value>sun</value>
         <value>sun</value>
      </set>
     </property>
  </bean>  
</beans>

ClientLogic.java

package java4s;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

public class ClientLogic {
    
    public static void main(String[] args)
    {
        Resource res = new ClassPathResource("spconfig.xml");
        BeanFactory factory = new XmlBeanFactory(res);
        
        Object o = factory.getBean("id1");
        WelcomeBean wb = (WelcomeBean)o;
        
        wb.show();
        
    }

}

Note:  Set wont allows duplicates, though you give duplicate values in spconfig.xml it will shows values only once in the output try this 😉

OutPut

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.