CODEWITHSUNDEEP
javaspringcode-injection
Will
Will

Reputation: 8631

Injection of constructor attributes

I'm injecting in a list which will populate a map used within the class.

However when injecting in the flowing attribute:

private List<?> srcSystemIDList;

via the flowing XML:

<bean id="transformerHelper" class="com.common.TransformerHelper">
        <property name="srcSystemIDList" value="#{ T(java.util.Arrays).asList('6','57','92','93','7','108','106','105','98','52','122','9','26','51','101','102','118') }" />
</bean>

which is used by this method to set the map: 

    public void srcSystemIDListInit()
{
        Object[] srcSystemArray = srcSystemIDList.toArray();
        int j;
        for(int i = 0; i< srcSystemArray.length; i = i+2)
        {
            j = i + 1;

            if(j < srcSystemArray.length)
            {
                srcSystemIDMap.put(srcSystemArray[i].toString(), srcSystemArray[j].toString());
            }
        }
}

I'm calling this via the constructor. 

public TransformerHelper()
{
    srcSystemIDListInit();
}

However when the constructor calls the method the list is null throwing a null pointer exception.

How can I populate the map via the injected list

Upvotes: 1

Views: 179

Answers (4)

nicholas.hauschild
nicholas.hauschild

Reputation: 42849

You can do as Vikdor says, or you have a couple other approaches you can take too.

  1. You could call this method, not from the constructor, but from your setter method setSrcSystemIDList(...). This will require the least work. (But really, all of these suggestions are quite easy...)
  2. You could implement the InitializingBean interface, and call your method from there.
  3. You could annotate the method with @PostConstruct.
  4. You could add an init-method attribute to your bean xml, which specifies the method to call.

Upvotes: 2

Anders R. Bystrup
Anders R. Bystrup

Reputation: 16060

You should have a look at something like this

<bean id="transformerHelper" class="com.common.TransformerHelper">
    <constructor-arg><ref bean="yourListBean"></constructor-arg>
</bean>

Visit the Source for more info.

Cheers,

Upvotes: 0

DRCB
DRCB

Reputation: 2121

You can either call initialization from property setter:

public void setSrcSystemIDList(List<?> srcSystemIDList) {
    this.srcSystemIDList = srcSystemIDList;
    srcSystemIDListInit();
}

And use your spring configuration as is.

Or define a constructor with parameters:

public TransformerHelper(List<?> srcSystemIDList) {
    this.srcSystemIDList = srcSystemIDList;
    srcSystemIDListInit();
}

And transfer the list as constructor argument in spring configuration:

<bean id="transformerHelper" class="com.common.TransformerHelper">
       <constructor-arg value="#{  T(java.util.Arrays).asList('6','57','92','93','7','108','106','105','98','52','122','9','26','51','101','102','118') }" />
</bean>

Upvotes: 1

Vikdor
Vikdor

Reputation: 24124

If you want to inject through constructor, then you should declare your constructor as

public TransformerHelper(List<?> srcSystemIDList)
{
    this.srcSystemIDList = srcSystemIDList;
    srcSystemIDListInit();
}

and your bean definition should be 

<bean id="transformerHelper" class="com.common.TransformerHelper">
    <constructor-arg value="#{ T(java.util.Arrays).asList('6','57','92','93','7','108','106','105','98','52','122','9','26','51','101','102','118') }" />
</bean>

Upvotes: 2

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