Thymeleaf th:href 参数中的条件 [英] Conditions in Thymeleaf th:href parameter

问题描述

所以我的 Thymeleaf 模板中有一个元素，它有一个看起来像这样的链接:

So I have an element in my Thymeleaf template which has a link looking like that:

th:href="@{'/search/'+${searchType}(parameter1=${parameter1}, ... parameter10=${parameter10})}"

根据当前的实现，parameter1...10 可以具有我不想包含在 href 中的值.比如如果是id，可以是-1，表示没有选择id，所以这个参数要省略，以免乱码url字符串，所以用

According to the current implementation the parameter1...10 can have values that I don't want to include in the href. For example, if it's id, it can be -1, which means that no id chosen, so this parameter have to be omitted to avoid clattering the url string, so instead of

/search/type?parameter1=-1

保持干净

/search/type

如何实现?我试过这个:

How this can be achieved? I tried this:

th:href="@{'/search/'+${searchType}((${parameter1}=='-1'?''parameter1=${parameter1}))}"

但是这个表达式会导致异常:

But this expression causes exception:

org.thymeleaf.exceptions.TemplateProcessingException:无法解析作为表达式:

org.thymeleaf.exceptions.TemplateProcessingException: Could not parse as expression:

我试过了:

th:href="@{'/search/'+${searchType}(parameter1=(${parameter1}=='-1'?'':${parameter1}))}"

但是结果还是不能接受:

But then the result is still not acceptable:

/search/type?parameter1=

那么从 url 中消除不需要的参数的正确方法是什么?

So what is the correct way to eliminate undesirable parameters from the url?

推荐答案

看来我做了更多的研究并找到了方法.关键词是:预处理.这是链接.因此，出于我的目的，以下表达式有效:

Looks like I did more research and found a way. The key word is: preprocessing. This is the link. So for my purposes the following expression works:

th:href="@{'/search/'+${searchType}(__(${parameter1}=='-1'?','parameter1=${parameter1})__,__(${parameter2}=='-1'?','parameter2=${parameter2})__)}"

简短说明:用双下划线包围表达式__(${parameter1}=='-1'?','parameter1=${parameter1})__，然后被包围的表达式将仅当它评估为非空字符串时才添加.在 url 参数的情况下，',' 计算为两个空参数并且不添加.

Short explanation: surround the expression with double underscores __(${parameter1}=='-1'?','parameter1=${parameter1})__, and then the surrounded expression will only be added if it evaluates to non-empty string. In the case of url parameters ',' evaluates to two empty parameters and not added.

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