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# Apache JSTL Module
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A dependency aggregation module for Eclipse Jetty that bundles Apache JSTL (JavaServer Pages Standard Tag Library) dependencies, enabling JSP tag library functionality in Jetty-based web applications. This module provides a JAR packaging solution for JSTL integration that is compatible with Jetty's modular architecture.
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## Package Information
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- **Package Name**: apache-jstl
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- **Package Type**: Maven
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- **Group ID**: org.eclipse.jetty
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- **Language**: Java
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- **Installation**: Include in Maven `pom.xml` dependencies
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## Maven Dependency
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```xml
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<dependency>
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    <groupId>org.eclipse.jetty</groupId>
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    <artifactId>apache-jstl</artifactId>
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    <version>11.0.0</version>
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</dependency>
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```
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## Basic Usage
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### Jetty Module Activation
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Enable JSTL support in Jetty by activating the module:
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```bash
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java -jar jetty-start.jar --module=apache-jstl
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```
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### JSP Page Integration
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Use JSTL tags in JSP pages by declaring the tag library:
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```jsp
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<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
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<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
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<!-- Example: URL generation with parameters -->
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<c:url value="/ref.jsp" var="refUrl">
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    <c:param name="id" value="123"/>
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</c:url>
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<!-- Example: Exception handling -->
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<c:catch var="catchException">
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    <fmt:parseNumber var="parsedNum" value="invalid_number" />
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</c:catch>
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<c:if test="${catchException != null}">
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    Error occurred: ${catchException.message}
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</c:if>
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```
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## Architecture
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This module follows Jetty's dependency aggregation pattern:
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- **JAR Wrapper**: Packages external JSTL dependencies into a single JAR for Maven compatibility
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- **Module Integration**: Provides Jetty module descriptor for seamless integration
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- **Container JAR Pattern**: Configures container include patterns for proper classpath loading
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- **Test Infrastructure**: Includes validation tests for JSTL functionality
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The module addresses Maven Dependency plugin limitations by providing JAR packaging for what is essentially a dependency collection, enabling Jetty's modular system to properly copy and include JSTL libraries.
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## Capabilities
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### JSTL Core Tag Library
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Provides core JSTL functionality including conditionals, loops, URL manipulation, and exception handling through the `http://java.sun.com/jsp/jstl/core` tag library.
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```java { .api }
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// JSP Tag Library URI
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String CORE_TAGLIB_URI = "http://java.sun.com/jsp/jstl/core";
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// Key tags available:
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// <c:url> - URL generation and encoding
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// <c:param> - URL parameter addition  
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// <c:catch> - Exception handling
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// <c:if> - Conditional processing
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// <c:set> - Variable assignment
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// <c:out> - Output with escaping
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```
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[JSTL Core Tags](./jstl-core.md)
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### JSTL Formatting Tag Library
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Provides internationalization and formatting capabilities through the `http://java.sun.com/jsp/jstl/fmt` tag library for number, date, and message formatting.
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```java { .api }
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// JSP Tag Library URI  
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String FMT_TAGLIB_URI = "http://java.sun.com/jsp/jstl/fmt";
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// Key tags available:
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// <fmt:parseNumber> - Number parsing with locale support
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// <fmt:formatNumber> - Number formatting
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// <fmt:parseDate> - Date parsing
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// <fmt:formatDate> - Date formatting
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// <fmt:message> - Internationalized messages
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```
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[JSTL Formatting](./jstl-formatting.md)
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### Jetty Integration Utilities
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Configuration utilities for integrating JSTL with Jetty WebAppContext, including container include patterns and temporary directory setup.
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```java { .api }
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public class JspConfig {
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    /**
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     * Initialize WebAppContext for JSP and JSTL processing.
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     *
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     * @param context WebAppContext to configure
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     * @param baseUri Base URI for the web application  
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     * @param scratchDir Temporary directory for JSP compilation
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     */
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    public static void init(WebAppContext context, URI baseUri, File scratchDir);
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}
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```
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[Jetty Integration](./jetty-integration.md)
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## Bundled Dependencies
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This module aggregates the following external dependencies:
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- **jakarta.servlet.jsp.jstl-api**: JSTL API specifications
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- **taglibs-standard**: Apache JSTL implementation (Morpher Jasper taglibs-standard)
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## Types
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```java { .api }
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// Core Jetty types for configuration
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class WebAppContext {
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    void setAttribute(String name, Object value);
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    void setWar(String war);
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    void setResourceBase(String resourceBase);
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}
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// Standard Java types for configuration
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class URI {
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    String toASCIIString();
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}
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class File {
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    // Standard file operations
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}
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```