Using Thymeleaf when the value is null

问题:

I have some values in my database which can be null if they have not already been entered.

But when I use Thymeleaf in my html, it gives an error when parsing null values.

Is there any way to handle this?

回答1:

The shortest way is using '?' operator. If you have User entity with embedded Address entity in order to access fields of Address entity and print them if address is not null, otherwise here will be an empty column:

<td th:text="${user?.address?.city}"></td>

回答2:

Sure there is. You can for example use the conditional expressions. For example:

<span th:text="${someObject.someProperty != null} ? ${someObject.someProperty} : 'null value!'">someValue</span>

You can even omit the "else" expression:

<span th:text="${someObject.someProperty != null} ? ${someObject.someProperty}">someValue</span>

You can also take a look at the Elvis operator to display default values.

回答3:

You can use 'th:if' together with 'th:text'

<span th:if="${someObject.someProperty != null}" th:text="${someObject.someProperty}">someValue</span>

回答4:

You've done twice the checking when you create

${someObject.someProperty != null} ? ${someObject.someProperty}

You should do it clean and simple as below.

<td th:text="${someObject.someProperty} ? ${someObject.someProperty} : 'null value!'"></td>

回答5:

   <p data-th-text ="${#strings.defaultString(yourNullable,'defaultValueIfYourValueIsNull')}"></p>

回答6:

This can also be handled using the elvis operator ?: which will add a default value when the field is null:

<span th:text="${object.property} ?: 'default value'"></span>

回答7:

Also worth to look at documentation for #objects build-in helper: https://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#objects

There is useful: ${#objects.nullSafe(obj, default)}

回答8:

I use

<div th:text ="${variable != null} ? (${variable != ''} ? ${variable} : 'empty string message') : 'null message' "></div>