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JSP tags
JSTL: A set of tag libraries developed by java itself, which can be used in JSP pages for you to simplify and beautify the code of JSP pages. It also has various statements such as loop, judgment, and ternary, which are mixed with el expressions. Generally, after we use jstl and el expressions, we can't see the java code on the jsp page.
If you want to use the jstl tag library, you have to check whether there are jstl packages in the packages that maven depends on:
If you don't have the jstl package, you have to import it yourself:
First go to the maven central library to bring in the dependencies of jstl;
If the import fails, then I will put the downloaded package into the lib under WEB-INF, and then addtobuild,
Then if you want to use the jstl tag library in the jsp page, first import the jstl tag library with the taglib command:
Jstl tag library learning:
1. Expression tags: out, set, remove, catch
2. Process markers: if (no else, single-way), choose (multi-way-when, otherwise)
3. Loop tokens: forEach, forTokens
Set tag:
You can also assign values to properties in an object:
If you use the el expression to output directly, there is no way to filter out the html code:
If you use out to output, it can be filtered, it will filter the html code into entities:
Of course, the above is the filtering effect of out output. If you don't want to filter, you can use escapeXml to set it to false for filtering:
You can also output default values for some properties that don't have them (the same effect can be achieved with ternary):
This remove can be used to delete stored property values.
Catch can be used to capture exception information, and then print out exception error information later.
The single-way condition if judgment is as shown above.
There are also multiple conditional judgments:
Multi-way conditional judgment, during which you can also use the if statement to make conditional judgments.
Use jstl and el expressions to change the index.jsp page: