返回的值为undefined
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
String path=request.getContextPath();
String basePath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>图书查询</title>
</head>
<body>
<center>
<h1>图书查询</h1>
<p>
图书ID：<input type="text" name="bookID">
图书名：<input type="text" name="bookName">
分类：<input type="text" name="catgoryName">
<input type="submit" value="查询" id="search">
</p>
<hr>
<table width="800px" cellspacing="0px" cellpadding="0px" border="1px">
<thead>
<tr>
<th>图书ID</th>
<th>书名</th>
<th>分类</th>
<th>价格</th>
<th>描述</th>
</tr>
</thead>
<tbody id="cont">
<c:forEach var="m" items="${books}">
<tr>
<td>${m.id }</td>
<td>${m.name }</td>
<td>${m.classname }</td>
<td>${m.price }</td>
<td>${m.description }</td>
</tr>
</c:forEach>
</tbody>
</table>
</center>
<script type="text/javascript" src="<%=basePath%>js/jquery-3.3.1.js"></script>
<script type="text/javascript">
$("#search").click(function(){
//单击查询按钮的时候触发ajax事件
$.ajax({
url:"<%=basePath%>SelectBookServlet" ,
type:"post",
data:{
bookID:$("input[name=bookID]").val(),
bookName:$("input[name=bookName]").val(),
catgoryName:$("input[name=catgoryName]").val()
},
dataType:"json",
success:function(result){//result里封装了servlet给ajax返回的结果
var list= eval(result);
console.log(list);
var s = null;
for (var i in list){
var id = list[i].id;
var bookName = list[i].name;
var bookCategory = list[i].classname;
var price = list[i].price;
var description = list[i].description;
s = s+ "<tr><td>" + id +"</td><td>"+bookName+"</td><td>"+bookCategory+"</td><td>"+price+"</td><td>"+
description+ "</td></tr>";
$("#cont>tr").remove();
}
$("#cont").html(s);
}
});
});
</script>
</body>
</html>
package wust.model;
public class Book {
private String id;
private String name;
private String classname;
private String price;
private String description;
public Book() {
}
public Book(String id, String name, String classname, String price, String description) {
super();
this.id = id;
this.name = name;
this.classname = classname;
this.price = price;
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getClassname() {
return classname;
}
public void setClassname(String classname) {
this.classname = classname;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Override
public String toString() {
return "Book [id=" + id + ", name=" + name + ", classname=" + classname + ", price=" + price + ", description="
+ description + "]";
}
}package wust.servlet;
import java.io.IOException;
import java.util.List;
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 org.json.JSONArray;
import wust.dao.LibDaoImpl;
import wust.model.Book;
/**
* Servlet implementation class SelectBookServlet
*/
@WebServlet("/SelectBookServlet")
public class SelectBookServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public SelectBookServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
LibDaoImpl libdaoimpl=new LibDaoImpl();
String bookID=request.getParameter("bookID");
String bookName=request.getParameter("bookName");
String catgoryName=request.getParameter("catgoryName");
if(bookID==null&&bookName==null&&catgoryName==null) {
List<Book> books=libdaoimpl.getBooksByCondition(null,null,null);
request.setAttribute("books", books);
request.getRequestDispatcher("/showBooks.jsp").forward(request, response);
}
else {
List<Book> books=libdaoimpl.getBooksByCondition(bookID, bookName, catgoryName);
JSONArray jsonArray = new JSONArray(books);
System.out.println(jsonArray);
response.getOutputStream().write(jsonArray.toString().getBytes("utf-8"));
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
doGet(request, response);
}
}json能正确返回，但是显示是undefined。
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2回答
好帮手慕阿莹
2019-02-26 10:01:38
老师用同学的代码测试着没有问题：
因为老师没有你的LibDaoImpl类，这里自己写了一个集合模拟查询结果。
建议同学试试自己写一个固定的集合，看看是否能读取出来呢？
老师测试的代码如下，同学也可以拿去试一下，如果这个没有问题，可能就是LibDaoImpl返回值的格式出了问题。建议同学检查一下。
package wust.servlet;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
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 org.json.JSONArray;
import wust.model.Book;
/**
* Servlet implementation class SelectBookServlet
*/
@WebServlet("/SelectBookServlet")
public class SelectBookServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public SelectBookServlet() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String bookID=request.getParameter("bookID");
String bookName=request.getParameter("bookName");
String catgoryName=request.getParameter("catgoryName");
if(bookID==null&&bookName==null&&catgoryName==null) {
List<Book> books=new ArrayList<Book>();
Book book = new Book("1","2","3","4","5");
Book book1 = new Book("你好","22","33","44","55");
Book book2 = new Book("111","222","333","444","555");
books.add(book);
books.add(book1);
books.add(book2);
request.setAttribute("books", books);
request.getRequestDispatcher("/showBooks.jsp").forward(request, response);
}
else {
List<Book> books=new ArrayList<Book>();
Book book = new Book("1","2","3","4","5");
Book book1 = new Book("你好","22","33","44","55");
books.add(book);
books.add(book1);
JSONArray jsonArray = new JSONArray(books);
System.out.println(jsonArray);
response.getOutputStream().write(jsonArray.toString().getBytes("utf-8"));
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
doGet(request, response);
}
}如果我的回答解决了你的疑惑，请采纳！祝学习愉快！
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