在 Freemarker 处理空值

如何在 Freemarker 中处理 null值？当 null值出现在数据中时，模板中会出现一些异常。

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最佳答案

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

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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.

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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"}
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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>
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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.

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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:


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