Handling null values in Freemarker

Question

How to handle null values in Freemarker? I get some exceptions in the template when null values are present in data.

Commove

Possible Duplicate: #307232 – Fibrilla

Answer 1

You can use the ?? test operator:

This checks if the attribute of the object is not null:

<#if object.attribute??></#if>

This checks if object or attribute is not null:

<#if (object.attribute)??></#if>

Source: FreeMarker Manual

Carlo

What is the difference between this approach and has_content ?? – Commove

has_content, next to null-checking, also checks if the value is not empty. This works for strings, sequences, hashes or collections. If the object is a date, boolean or a number, then it acts as non-empty. For all other types it will act as empty. – Carlo

I have this problem where I have to check if the value in bean is null.I tried the following:${checknull(Bean.getValue())}, where checknull if a function <#function checknull x> <#if x??> <#return ""> <#else> <#return x> </#if> </#function> but I get "Error executing macro: checknull required parameter: x is not specified." error – Commove

You have to reverse the returns: <#function checknull x> <#if x??> <#return x> <#else> <#return ""> </#if> </#function> – Carlo

Please check below answer: https://mcmap.net/q/204064/-handling-null-values-in-freemarker – Horal

@TomVerelst what if I want to check if both the object and attribute are not null? – Kitchenette

Answer 2

Starting from freemarker 2.3.7, you can use this syntax :

${(object.attribute)!}

or, if you want display a default text when the attribute is null :

${(object.attribute)!"default text"}

Commensurable

For those who are using Freemarker as template engine for XDocReport, this is working after adding <dependency><groupId>org.freemarker</groupId><artifactId>freemarker</artifactId><version>2.3.22</version></dependency> to your pom.xml. – Clo

How do you do it if you have a date and the date could be null? In other words object.dateAcquired where dateAcquired could be null and you have ${object.dateAcquired?date} – Bundesrat

@StephaneGrenier use ${(object.dateAcquired?date)!"not present"} – Depurate

Great example. Helped me alot. The bracket, however are obsolet. ${salutation!'Dear Mr. or Mrs.'} – Niersteiner

Any idea how could I print .now?long on default value? – Flagitious

Answer 3

I think it works the other way

<#if object.attribute??>
   Do whatever you want....
</#if>

If object.attribute is NOT NULL, then the content will be printed.

Cortie

If object is nullable also then we can use (object.attribute)?? – Spokane

Answer 4

Use ?? operator at the end of your <#if> statement.

This example demonstrates how to handle null values for two lists in a Freemaker template.

List of cars:
<#if cars??>
    <#list cars as car>${car.owner};</#list>
</#if>
List of motocycles:
<#if motocycles??>
    <#list motocycles as motocycle>${motocycle.owner};</#list>
</#if>

Leprosarium

Answer 5

I would like to add more context if you have issues and this is what I have tried.

<#if Recipient.account_type?has_content>
  … (executes if variable exists)
<#else>
  … (executes if variable does not exist)
</#if>

This is more like Javascript IF and ELSE concept where we want to check whether this value or another chaining through required logic.

Freemarker webite

Other reference:

Scenario: Customer has ID and name combined like 13242 Harish, so where our stakeholder need the only name, so I have tried this ${record.entity?keep_after(" ")} and it did work, however, it can only work when you have space, but when a customer doesn't have space and one name, I had to do some IF ELSE condition to check Null value.

Hendren

Answer 6

Use:

${(user.isSuperman!false)?c}

It will work when "isSuperman" is null and when have boolean value

What we want:

• For "null" we want to output 'false'
• For boolean value and want to output value ('true' or 'false')

What we know:

• boolean need to convert to string by using "?c" see Built-ins for booleans
• but null we cannot convert to string and we need to use "!" see Handling missing values

Pademelon

Here what happens if the user is null? – Kitchenette

@bee I think it will be an exception and I suggest we need to use extra circle brackets as ${((user.isSuperman)!false)?c}. Just test to be sure. – Pademelon

Yes, that's what's worked. Thanks. – Kitchenette