Memories are often easy to forget, or write down in one place is more appropriate. ———— Notes

Spring supports injecting values into four collection types, which are:

• List – <list/>
• Set – <set/>
• Map – <map/>
• Properties – <props/>

Spring beans

The following is a Customer class with four collection attributes:

package com.mkyong.common;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class Customer
{
    private List<Object> lists;
    private Set<Object> sets;
    private Map<Object, Object> maps;
    private Properties pros;

    //...
}

Next, let's look at how to declare these collections in XML.

1. List collection

<property name="lists">
    <list>
        <value>1</value>
        <ref bean="PersonBean" />
        <bean class="com.mkyong.common.Person">
            <property name="name" value="mkyongList" />
            <property name="address" value="address" />
            <property name="age" value="28" />
        </bean>
    </list>
</property>

2. Set sets

<property name="sets">
    <set>
        <value>1</value>
        <ref bean="PersonBean" />
        <bean class="com.mkyong.common.Person">
            <property name="name" value="mkyongSet" />
            <property name="address" value="address" />
            <property name="age" value="28" />
        </bean>
    </set>
</property>

3. Map collection

<property name="maps">
    <map>
        <entry key="Key 1" value="1" />
        <entry key="Key 2" value-ref="PersonBean" />
        <entry key="Key 3">
            <bean class="com.mkyong.common.Person">
                <property name="name" value="mkyongMap" />
                <property name="address" value="address" />
                <property name="age" value="28" />
            </bean>
        </entry>
    </map>
</property>

4. Properties collection

<property name="pros">
    <props>
        <prop key="admin">admin@nospam.com</prop>
        <prop key="support">support@nospam.com</prop>
    </props>
</property>

5. Complete configuration

<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="CustomerBean" class="com.mkyong.common.Customer">

        <!-- java.util.List -->
        <property name="lists">
            <list>
                <value>1</value>
                <ref bean="PersonBean" />
                <bean class="com.mkyong.common.Person">
                    <property name="name" value="mkyongList" />
                    <property name="address" value="address" />
                    <property name="age" value="28" />
                </bean>
            </list>
        </property>

        <!-- java.util.Set -->
        <property name="sets">
            <set>
                <value>1</value>
                <ref bean="PersonBean" />
                <bean class="com.mkyong.common.Person">
                    <property name="name" value="mkyongSet" />
                    <property name="address" value="address" />
                    <property name="age" value="28" />
                </bean>
            </set>
        </property>

        <!-- java.util.Map -->
        <property name="maps">
            <map>
                <entry key="Key 1" value="1" />
                <entry key="Key 2" value-ref="PersonBean" />
                <entry key="Key 3">
                    <bean class="com.mkyong.common.Person">
                        <property name="name" value="mkyongMap" />
                        <property name="address" value="address" />
                        <property name="age" value="28" />
                    </bean>
                </entry>
            </map>
        </property>

        <!-- java.util.Properties -->
        <property name="pros">
            <props>
                <prop key="admin">admin@nospam.com</prop>
                <prop key="support">support@nospam.com</prop>
            </props>
        </property>

    </bean>

    <bean id="PersonBean" class="com.mkyong.common.Person">
        <property name="name" value="mkyong1" />
        <property name="address" value="address 1" />
        <property name="age" value="28" />
    </bean>

</beans>

Run it:

package com.mkyong.common;

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

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

        Customer cust = (Customer)context.getBean("CustomerBean");
        System.out.println(cust);

    }
}

Output:

Customer [

lists=[
1,
Person [address=address 1, age=28, name=mkyong1],
Person [address=address, age=28, name=mkyongList]
],

maps={
key 1=1,
key 2=Person [address=address 1, age=28, name=mkyong1],
key 3=Person [address=address, age=28, name=mkyongMap]
},

pros={admin=admin@nospam.com, support=support@nospam.com},

sets=[
1,
Person [address=address 1, age=28, name=mkyong1],
Person [address=address, age=28, name=mkyongSet]]
]

Code download address: http://www.mkyong.com/wp-content/uploads/2010/03/Spring-Collection-Example.zip

Translation: https://www.mkyong.com/spring/spring-collections-list-set-map-and-properties-example/