CODEWITHSUNDEEP
spring
Bastl
Bastl

Reputation: 1471

how to extend a list in spring config

I have defined a with some "common" values. How can I extend the common list by additional values to various new beans?

<util:list id="myCommonList" list-class="java.util.LinkedList">
 <bean .../>
 <bean .../>
 <bean .../>
 <bean .../>
</util:list>


<bean id="extension" parent="myCommonList">
  <bean ref="additionalValue"/>
</bean>

Will this overwrite the list or extend it?

Upvotes: 23

Views: 29448

Answers (6)

adrock20
adrock20

Reputation: 327

To append list2's elements to list1 use the following spring config.

<util:list id="list1">
    <value>1</value>
<util:list>

<util:list id="list2">
    <value>3</value>
    <value>5</value>
<util:list>

<bean
    class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
    <property name="targetObject" ref="list1" />
    <property name="targetMethod" value="addAll" />
    <property name="arguments" ref="list2" />
</bean>

Upvotes: 4

Nani
Nani

Reputation: 1

You can overwrite or add any other bean in this list by following the below snippet.

For example: this is your bean which needs to be injected in the AAA util:list mentioned below.

<bean id = "BBB" class=""/>
<util:list id="AAA"/>
<bean id="AAAListMergeDirective" depends-on="AAA" 
parent="listMergeDirective" >
<property name="add" ref="BBB"  />
</bean>

Upvotes: 0

Bird Bird
Bird Bird

Reputation: 430

Based on skaffman's answer, you can achive this way:

<util:list id="parent">
    <value>X</value>
</util:list>

<bean id="child" parent="parent" class="org.springframework.beans.factory.config.ListFactoryBean">
    <property name="sourceList">
        <list merge="true">
            <value>Y</value>
        </list>
    </property>
</bean>

Upvotes: 11

Mikhail Tsaplin
Mikhail Tsaplin

Reputation: 642

Today I was having this issue too. For me the acceptable solution was to use SpEL and while SpEL doesn't supports multiple statements - create two auxiliary classes that appends lists.

Context might be implemented like this:

<util:list id="list1">
    <value>str1</value>
    <value>str2</value>
</util:list>

<util:list id="list2">
    <value>str3</value>
    <value>str4</value>
</util:list>

<bean ...>
    <property name="propertyThatRequiresMergedList"
        value="#{ new x.y.springs.StringListsMerger().merge(@list1, @list2) }" />
</bean>

And classes:

package x.y.springs;

import java.util.List;

public abstract class ListsMerger<T extends List> {
    public T merge(T ... lists) {
        T container = createContainer();
        for (T list : lists) {
            container.addAll(list);
        }
        return container;
    }
    public abstract T createContainer();
}


package x.y.springs;

import java.util.ArrayList;
import java.util.List;

public class StringListsMerger extends ListsMerger<List<String>> {

    @Override
    public List<String> createContainer() {
        return new ArrayList<String>();
    }

}

Upvotes: 1

abalogh
abalogh

Reputation: 8281

According to this JIRA; there is no trivial solution for this (currently, but hopefully in 3.1 there will be), though there are several workarounds; e.g. this one.

Upvotes: 2

skaffman
skaffman

Reputation: 403581

You can do it, but not using <util:list>, which is just a convenience syntax. The container does provide a "collection merging" function, but you have to use the "old" style:

<bean id="parent" class="org.springframework.beans.factory.config.ListFactoryBean">
    <property name="sourceList">
        <list>
            <value>X</value>
        </list>
    </property>
</bean>

<bean id="child" parent="parent" class="org.springframework.beans.factory.config.ListFactoryBean">
    <property name="sourceList">
        <list merge="true">
            <value>Y</value>
        </list>
    </property>
</bean>

Upvotes: 36

Related Questions