JSTL标签出错：

今天在运行书里的JSTL标签代码的时候出错，总结一下：

问题1.The JSP specification requires that an attribute name is preceded by whitespace

解决：<c:forEach var="book" items="${requestScope.books}"varStatus="status">出错

改为：<c:forEach var="book" items="${requestScope.books}" varStatus="status">

原因：varStatus="status"前加空格

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问题2.Property 'isbn' not found on type java.lang.String

解决：<c:forEach var="book" items=" ${requestScope.books}" varStatus="status">出错

改为：<c:forEach var="book" items="${requestScope.books}" varStatus="status">

原因：${requestScope.books}前去掉空格

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问题3.程序能运行了,jsp能访问，但是EL表达式读取不到想要的信息   

解决：没有在.xml配置文件添加servlet的<url-pattern>信息，无法调用servlet向jsp传对象。

在.xml文件中添加：

<servlet>
   <servlet-name>BooksServlet</servlet-name>
   <servlet-class>com.controller.BooksServlet</servlet-class>
</servlet>
<servlet-mapping>
   <servlet-name>BooksServlet</servlet-name>
   <url-pattern>/BooksServlet</url-pattern>
</servlet-mapping>

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jstl标签练习代码：

1.BooksServlet.java

 package com.controller;
 import java.io.IOException;
 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 java.util.List;
 import java.util.ArrayList;
 import com.model.Book;
 //@WebServlet("/BooksServlet")
  public class BooksServlet extends HttpServlet {
     @Override
     public void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
        List<Book> books = new ArrayList<Book>();
        Book book1 = new Book("978-7-302-23059-5","Java语言程序设计",45.00);
        Book book2 = new Book("978-7-302-21540-0","Java Web编程技术",39.00);
        Book book3 = new Book("978-7-302-24130-0","C #入门经典",99.80);
        books.add(book1);
        books.add(book2);
        books.add(book3);
        request.setAttribute("books", books);
        RequestDispatcher rd = request.getRequestDispatcher("/books.jsp");
        rd.forward(request, response);
       }
 }

2.Book.java（javaBean类）

 package com.model;

 public class Book {
    private String isbn;
    private String title;
    private double price;
    public Book(String isbn, String title, double price) {
     super();
     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;
     }

 }

3.books.jsp

 package com.model;

 public class Book {
    private String isbn;
    private String title;
    private double price;
    public Book(String isbn, String title, double price) {
     super();
     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;
     }

 }

4.配置文件.xm

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
   <display-name>Ex_JSTL_tag</display-name>
   <servlet>
     <servlet-name>BooksServlet</servlet-name>
     <servlet-class>com.controller.BooksServlet</servlet-class>
   </servlet>
   <servlet-mapping>
     <servlet-name>BooksServlet</servlet-name>
     <url-pattern>/BooksServlet</url-pattern>
   </servlet-mapping>
   <welcome-file-list>
     <welcome-file>index.html</welcome-file>
     <welcome-file>index.htm</welcome-file>
     <welcome-file>books.jsp</welcome-file>
     <welcome-file>default.htm</welcome-file>
     <welcome-file>default.jsp</welcome-file>
   </welcome-file-list>
 </web-app>

5.运行时注意加入   http://localhost/Ex_JSTL_tag/BooksServlet

只有在url中加入/BooksServlet才能调用到servlet想jsp传参数

截图：

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