Spring: Inject map of beans (key and value both are beans)

In my previous post, I explained how to inject map, where key is an integer and value is pointed to a bean. In this post, I am going to explain how to inject a map where key and value are beans.

By using <map>, <entry> elements, key-ref and value-ref attributes, you can inject map of beans.

Example

 <bean id="countryInfo" name="countryInfo" class="com.sample.pojo.Countries">
  <property name="countriesMap">
   <map>
    <entry key-ref="india" value-ref="indiaInfo" />
    <entry key-ref="russia" value-ref="russiaInfo" />
   </map>
  </property>
 </bean>

Following is the complete working application.

Country.java

package com.sample.pojo;

public class Country {
 private String name;
 private String capital;

 public String getName() {
  return name;
 }

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

 public String getCapital() {
  return capital;
 }

 public void setCapital(String capital) {
  this.capital = capital;
 }

 @Override
 public String toString() {
  StringBuilder builder = new StringBuilder();
  builder.append("Country [name=").append(name).append(", capital=").append(capital).append("]");
  return builder.toString();
 }

 @Override
 public int hashCode() {
  final int prime = 31;
  int result = 1;
  result = prime * result + ((capital == null) ? 0 : capital.hashCode());
  result = prime * result + ((name == null) ? 0 : name.hashCode());
  return result;
 }

 @Override
 public boolean equals(Object obj) {
  if (this == obj)
   return true;
  if (obj == null)
   return false;
  if (getClass() != obj.getClass())
   return false;
  Country other = (Country) obj;
  if (capital == null) {
   if (other.capital != null)
    return false;
  } else if (!capital.equals(other.capital))
   return false;
  if (name == null) {
   if (other.name != null)
    return false;
  } else if (!name.equals(other.name))
   return false;
  return true;
 }

}

CountryInformation.java

package com.sample.pojo;

public class CountryInformation {
 private String language;
 private String currency;

 public String getLanguage() {
  return language;
 }

 public void setLanguage(String language) {
  this.language = language;
 }

 public String getCurrency() {
  return currency;
 }

 public void setCurrency(String currency) {
  this.currency = currency;
 }

 @Override
 public String toString() {
  StringBuilder builder = new StringBuilder();
  builder.append("CountryInformation [language=").append(language).append(", currency=").append(currency)
    .append("]");
  return builder.toString();
 }

}

Countries.java

package com.sample.pojo;

import java.util.Map;

public class Countries {
 private Map<Country, CountryInformation> countriesMap;

 public Map<Country, CountryInformation> getCountriesMap() {
  return countriesMap;
 }

 public void setCountriesMap(Map<Country, CountryInformation> countriesMap) {
  this.countriesMap = countriesMap;
 }

}

myConfiguration.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="india" class="com.sample.pojo.Country">
  <property name="name" value="India" />
  <property name="capital" value="New Delhi" />
 </bean>

 <bean id="russia" class="com.sample.pojo.Country">
  <property name="name" value="Russia" />
  <property name="capital" value="Moscow" />
 </bean>

 <bean id="russiaInfo" class="com.sample.pojo.CountryInformation">
  <property name="language" value="Russian" />
  <property name="currency" value="Ruble" />
 </bean>


 <bean id="indiaInfo" class="com.sample.pojo.CountryInformation">
  <property name="language" value="Hindi" />
  <property name="currency" value="Rupee" />
 </bean>

 <bean id="countryInfo" name="countryInfo" class="com.sample.pojo.Countries">
  <property name="countriesMap">
   <map>
    <entry key-ref="india" value-ref="indiaInfo" />
    <entry key-ref="russia" value-ref="russiaInfo" />
   </map>
  </property>
 </bean>

</beans>

HelloWorld.java

package com.sample.test;

import java.util.Set;

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

import com.sample.pojo.Countries;
import com.sample.pojo.Country;

public class HelloWorld {
 public static void main(String args[]) {
  ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "myConfiguration.xml" });

  Countries countries = context.getBean("countryInfo", Countries.class);

  Set<Country> countrySet = countries.getCountriesMap().keySet();

  for (Country country : countrySet) {
   System.out.println(country + " : " + countries.getCountriesMap().get(country));
  }

  ((ClassPathXmlApplicationContext) context).close();
 }
}

Run ‘HelloWorld.java’, you can able to see following output.

Country [name=India, capital=New Delhi] : CountryInformation [language=Hindi, currency=Rupee]
Country [name=Russia, capital=Moscow] : CountryInformation [language=Russian, currency=Ruble]

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