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I know the life cycle of JSP page but i wondered when i started to use JSTL. My question is that in which phase of JSP life cycle this JSTL tags evaluates? for example in jsp translation phase or in service phase.
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JSTL stands for JSP Standard Tag Library. JSTL is the standard tag library that provides tags to control the JSP page behavior. JSTL tags can be used for iteration and control statements, internationalization, SQL etc.
During the translation phase each type of data in a JSP page is treated differently. Static data is transformed into code that will emit the data into the response stream. JSP elements are treated as follows: Directives are used to control how the web container translates and executes the JSP page.
The JSTL core tag provide variable support, URL management, flow control, etc. The URL for the core tag is http://java.sun.com/jsp/jstl/core. The prefix of core tag is c. The functions tags provide support for string manipulation and string length.
At translation phase
Custom tags are converted into calls to the tag handler that implements the custom tag.
When you execute that JSP (which happens after successful compilation(translation)), they actually run and render the output to response.
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JSTL is evaluated during JSP compilation (or translation) phase. You can check that by the stacktrace if an exception is thrown:
org.apache.jasper.JasperException: /index.jsp (line: 8, column: 23) No tag "urfafl" defined in tag library imported with prefix "c"
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:42)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:408)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:199)
org.apache.jasper.compiler.Parser.parseCustomTag(Parser.java:1215)
org.apache.jasper.compiler.Parser.parseElements(Parser.java:1452)
org.apache.jasper.compiler.Parser.parse(Parser.java:138)
org.apache.jasper.compiler.ParserController.doParse(ParserController.java:242)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:102)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:198)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:373)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
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