JSTL（JSP标准标签库）

JSP标准标签库（JavaServer Pages Tag Library, JSTL）是一个定制JSP标签库的集合，封装了JSP应用的通用核心功能。用来解决像遍历Map或集合、条件测试、XML处理，甚至数据库访问和数据操作等常见的问题。

使用JSTL前的准备

JSTL的相关jar包可以从Tomcat的官网下载

使用JSTL前需要把下面的JAR包放到 "/WEB-INF/lib" 目录下

- taglibs-standard-spec-1.2.5.jar
- taglibs-standard-impl-1.2.5.jar
- taglibs-standard-jstlel-1.2.5.jar
- xalan-2.7.1.jar
- serializer-2.7.1.jar

其 maven 坐标为

    <!-- https://mvnrepository.com/artifact/org.apache.taglibs/taglibs-standard-spec -->
    <dependency>
        <groupId>org.apache.taglibs</groupId>
        <artifactId>taglibs-standard-spec</artifactId>
        <version>1.2.5</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.taglibs/taglibs-standard-impl -->
    <dependency>
        <groupId>org.apache.taglibs</groupId>
        <artifactId>taglibs-standard-impl</artifactId>
        <version>1.2.5</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.taglibs/taglibs-standard-jstlel -->
    <dependency>
        <groupId>org.apache.taglibs</groupId>
        <artifactId>taglibs-standard-jstlel</artifactId>
        <version>1.2.5</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/xalan/xalan -->
    <dependency>
        <groupId>xalan</groupId>
        <artifactId>xalan</artifactId>
        <version>2.7.2</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/xalan/serializer -->
    <dependency>
        <groupId>xalan</groupId>
        <artifactId>serializer</artifactId>
        <version>2.7.2</version>
    </dependency>

xalan-2.7.1.jar和serializer-2.7.1.jar可从下面网站很方便下载得到，

进入Jar File Dowlaod后，根据字母排序找到想要的Jar包，下载即可。

根据JSTL标签所提供的功能，可以将其方位5个大类

在JSP页面中使用JSTL，必须通过下面的格式使用 taglib 指令

<%@ taglib uri="uri" prefix="prefix" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>       <!-- 核心标签 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>      <!-- 格式化标签 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %>      <!-- SQL标签 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>        <!-- XML标签 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %> <!-- JSTL函数 -->

JSTL中具体标签的详细说明可参见以下网站

https://www.runoob.com/jsp/jsp-jstl.html

截图概述

核心标签  <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

使用 <c:if> 判断属性的值，下面的代码为判断 requestScope 范围中的属性 taxid 的值是我否为 “taxid”

requestScope 是 EI 内置对象

test 只接受 boolean 值

<c:if test="${requestScope.taxid == 'taxid' }" >
    <th>taxId</th>
</c:if>

<c:if test="${requestScope.taxid != null }" >
    <th>taxId</th>
</c:if>

格式化标签  <%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>

SQL标签  <%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %>

XML标签  <%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>

JSTL函数  <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>

 

使用JSTL的例子

Servlet作为Controller

package app05a.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import app05a.model.Book;

@WebServlet(name = "BookServlet", urlPatterns = { "/books" })
public class BookServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public BookServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Book> books = new ArrayList<Book>();
        Book book1 = new Book("978-0980839616", "Java 7: A Beginner's Tutorial", 45.00);
        Book book2 = new Book("978-0980331608", "Structs 2 Design and programming: A Tutorial", 49.95);
        Book book3 = new Book("978-0975212820", "Dimensional Data Warehousing with MySQL: A Tutorial", 39.95);
        books.add(book1);
        books.add(book2);
        books.add(book3);
        request.setAttribute("books", books);
        RequestDispatcher rd = request.getRequestDispatcher("/books.jsp");
        rd.forward(request, response);
    }
}

JavaBean作为Model

package app05a.model;

public class Book {
    private String isbn;
    private String title;
    private double price;
    
    public Book() {}
    public Book(String isbn, String title, double price) {
        this.isbn = isbn;
        this.title = title;
        this.price = price;
    }
    
    public String getIsbn() {
        return isbn;
    }
    public void setisbn(String isbn) {
        this.isbn = isbn;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
}

package app05a.model;

public class Book {
    private String isbn;
    private String title;
    private double price;
    
    public Book() {}
    public Book(String isbn, String title, double price) {
        this.isbn = isbn;
        this.title = title;
        this.price = price;
    }
    
    public String getIsbn() {
        return isbn;
    }
    public void setisbn(String isbn) {
        this.isbn = isbn;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
}

JSP页面作为view

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Book List</title>
    <style>
        table, tr, td {
            border: 1px solid brown;
        }
    </style>
</head>
<body>
    Books in Simple table;
    <table>
        <tr>
            <td>ISBIN</td>
            <td>Title</td>
        </tr>
        <c:forEach items="${requestScope.books }" var="book">
            <tr>
                <td>${book.isbn }</td>
                <td>${book.title }</td>
            </tr>
        </c:forEach>
    </table>
    <br />
    Books in Styled Table
    <table>
        <tr style="background:#c0c0c0">
            <td>ISBN</td>
            <td>Title</td>
        </tr>
        <c:forEach items="${requestScope.books }" var="book" varStatus="status">
            <c:if test="${status.count % 2 == 0 }">  <!-- 偶数行 -->
                <tr style="background:#ffff00">
            </c:if>
            <c:if test="${status.count %2 != 0 }">  <!-- 奇数行 -->
                <tr style="background:#00ffff">
            </c:if>
            <td>${book.isbn }</td>
            <td>${book.title }</td>
        </c:forEach>
    </table>
    <br />
    ISBNs only:
    <c:forEach items="${requestScope.books }" var="book" varStatus="status">
        ${book.isbn } <c:if test="${!status.last }">,</c:if> <!-- 表明当前这轮迭代是否为最后一次迭代的标志 -->
    </c:forEach>
</body>
</html>

效果

使用<c:forEach>遍历Map

Servlet作为Controller

package app05a.servlet;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(name = "CitiesServlet", urlPatterns = { "/cities" })
public class CitiesServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public CitiesServlet() {
        super();
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Map<String, String> capitals = new HashMap<String, String>();
        capitals.put("Indonesia", "Jakarta");
        capitals.put("Thailand", "Bangkok");
        capitals.put("Malaysia", "Kuala Lumpur");
        request.setAttribute("capitals", capitals);
        
        Map<String, String[]> bigCities = new HashMap<>();
        bigCities.put("Australia", new String[] {"Sydney","Melbourne","Perth"});
        bigCities.put("New Zealand", new String[] {"Auchland","Christchurch","Wellington"});
        bigCities.put("Indonesia", new String[] {"Jakarta","Surabaya","Medan"});
        request.setAttribute("bigCities", bigCities);
        
        RequestDispatcher rd = request.getRequestDispatcher("/cities.jsp");
        rd.forward(request, response);
    }
}

JSP页面作为view

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Cities</title>
    <style>
        table, tr, td {
            border: 1px solid #aaee77;
            padding:3px;
        }
    </style>
</head>
<body>
    Capitals <br />
    <table>
        <tr style="background:#448755; color:white; font-weight:bold;">
            <td>Country</td>
            <td>Capital</td>
        </tr>
        <c:forEach items="${requestScope.capitals }" var="mapItem"> <!-- 遍历Map -->
            <tr>
                <td>${mapItem.key }</td>  <!-- 获取key -->
                <td>${mapItem.value }</td>  <!-- 获取value -->
            </tr>
        </c:forEach>
    </table>
    <br />
    Big Cities <br />
    <table>
        <tr style="background:#448755; color:white; font-weight:bold;">
            <td>Country</td>
            <td>BigCities</td>
        </tr>
        <c:forEach items="${requestScope.bigCities }" var="mapItem">
            <tr>
                <td>${mapItem.key }</td>
                <td>
                <c:forEach items="${mapItem.value }" var="city" varStatus="status"> <!-- Map的value是数组，也需要遍历 -->
                    ${city }<c:if test="${!status.last }">,</c:if>
                </c:forEach>
                </td>
            </tr>
        </c:forEach>
    </table>
</body>
</html>

效果