从数据库中检索数据在Java服务器页面中

huangapple
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英文:

Retrieve Data from Database in Java Server Page

问题

我试图从数据库中获取数据并在浏览器中打印出一个表格。代码位于一个 JSP 文件中。

我的输出如下所示：

从数据库中检索数据在Java服务器页面中

仍然缺少表中的值。现在我想知道为什么没有获取到表中的数据。我检查了数据，表中填充了值。

以下是带有数据的命令行输出（已模糊处理）：

从数据库中检索数据在Java服务器页面中

以下是我在 JSP 文件中的代码：

  1. <%@page contentType="text/html" pageEncoding="UTF-8"%>
  3. <%@page import="java.sql.DriverManager"%>
  4. <%@page import="java.sql.ResultSet"%>
  5. <%@page import="java.sql.Statement"%>
  6. <%@page import="java.sql.Connection"%>
  7. <%
  8.     String id = request.getParameter("userid");
  9.     String driver = "com.mysql.jdbc.Driver";
  10.     String connectionUrl = "jdbc:mysql://localhost:3306/";
  11.     String database = "store";
  12.     String userid = "root";
  13.     String password = "";
  14.     try {
  15.         Class.forName(driver);
  16.     } catch (ClassNotFoundException e) {
  17.         e.printStackTrace();
  18.     }
  19.     Connection connection = null;
  20.     Statement statement = null;
  21.     ResultSet resultSet = null;
  22. %>
  25. <!DOCTYPE html>
  26. <html>
  27.     <head>
  28.         <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  29.         <title>JSP Page</title>
  30.     </head>
  31.     <body>
  32.         <h1>Retrieve data from database in jsp</h1>
  33. 		<table border="1">
  34. 			<tr>
  35. 				<th>Name</th>
  36. 				<th>Strasse</th>
  37. 				<th>PLZ</th>
  38. 				<th>Ort</th>
  39. 			</tr>
  40. 			
  41. 			<%
  42. 				try{
  43. 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  44. 					statement=connection.createStatement();
  45. 					String sql ="select * from kunde";
  46. 					resultSet = statement.executeQuery(sql);
  47. 					while(resultSet.next()){
  48. 						%>
  49. 						<tr>
  50. 							<td><%=resultSet.getString("name") %></td>
  51. 							<td><%=resultSet.getString("strasse") %></td>
  52. 							<td><%=resultSet.getString("plz") %></td>
  53. 							<td><%=resultSet.getString("ort") %></td>
  54. 						</tr>
  55. 						
  56. 						<%
  57. 					}
  58. 					connection.close();
  59. 				}
  60. 				catch (Exception e) {
  61. 					e.printStackTrace();
  62. 				}
  63. 			%>
  64. 			</table>
  65.     </body>
  66. </html>

在日志文件中，我找到了两条以下错误消息：

  1. 在 jsp 文件中的第 [41] 行发生错误：[/index.jsp]
  2. 无法将 userid 解析为变量
  3. 38: 			
  4. 39: 			<%
  5. 40: 				try{
  6. 41: 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  7. 42: 					statement=connection.createStatement();
  8. 43: 					String sql ="select * from kunde";
  9. 44: 					resultSet = statement.executeQuery(sql);
  10. ...
  12. 堆栈跟踪，带有根本原因
  13. org.apache.jasper.JasperException: 无法为 JSP 编译类：
  15. 在 jsp 文件中的第 [41] 行发生错误：[/index.jsp]
  16. 无法将 userid 解析为变量
  17. 38: 			
  18. 39: 			<%
  19. 40: 				try{
  20. 41: 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  21. 42: 					statement=connection.createStatement();
  22. 43: 					String sql ="select * from kunde";
  23. 44: 					resultSet = statement.executeQuery(sql);
  24. ...

和

  1. [警告] 拒绝访问用户 'XY'@'localhost'（未使用密码）
英文:

i am trying to print out a table in the browser with fetching data from a database. The code is in a jsp-file.

My output looks the following:

从数据库中检索数据在Java服务器页面中

It is still missing the values from the table. Now i am wondering why the data from the table is not fetched. I checked the data, and the table is filled with values.

Here is my command-line output with data (blurred):
从数据库中检索数据在Java服务器页面中

This is my code in the jsp-file so far:

  1. &lt;%@page contentType=&quot;text/html&quot; pageEncoding=&quot;UTF-8&quot;%&gt;
  3. &lt;%@page import=&quot;java.sql.DriverManager&quot;%&gt;
  4. &lt;%@page import=&quot;java.sql.ResultSet&quot;%&gt;
  5. &lt;%@page import=&quot;java.sql.Statement&quot;%&gt;
  6. &lt;%@page import=&quot;java.sql.Connection&quot;%&gt;
  7. &lt;%
  8. 	String id = request.getParameter(&quot;userid&quot;);
  9. 	String driver = &quot;com.mysql.jdbc.Driver&quot;;
  10. 	String connectionUrl = &quot;jdbc:mysql://localhost:3306/&quot;;
  11. 	String database = &quot;store&quot;;
  12. 	String userid = &quot;root&quot;;
  13. 	String password = &quot;&quot;;
  14. 	try {
  15. 	Class.forName(driver);
  16. 	} catch (ClassNotFoundException e) {
  17. 	e.printStackTrace();
  18. 	}
  19. 	Connection connection = null;
  20. 	Statement statement = null;
  21. 	ResultSet resultSet = null;
  22. %&gt;
  25. &lt;!DOCTYPE html&gt;
  26. &lt;html&gt;
  27.     &lt;head&gt;
  28.         &lt;meta http-equiv=&quot;Content-Type&quot; content=&quot;text/html; charset=UTF-8&quot;&gt;
  29.         &lt;title&gt;JSP Page&lt;/title&gt;
  30.     &lt;/head&gt;
  31.     &lt;body&gt;
  32.         &lt;h1&gt;Retrieve data from database in jsp&lt;/h1&gt;
  33. 		&lt;table border=&quot;1&quot;&gt;
  34. 			&lt;tr&gt;
  35. 				&lt;th&gt;Name&lt;/th&gt;
  36. 				&lt;th&gt;Strasse&lt;/th&gt;
  37. 				&lt;th&gt;PLZ&lt;/th&gt;
  38. 				&lt;th&gt;Ort&lt;/th&gt;
  39. 			&lt;/tr&gt;
  40. 			
  41. 			&lt;%
  42. 				try{
  43. 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  44. 					statement=connection.createStatement();
  45. 					String sql =&quot;select * from kunde&quot;;
  46. 					resultSet = statement.executeQuery(sql);
  47. 					while(resultSet.next()){
  48. 						%&gt;
  49. 						&lt;tr&gt;
  50. 							&lt;td&gt;&lt;%=resultSet.getString(&quot;name&quot;) %&gt;&lt;/td&gt;
  51. 							&lt;td&gt;&lt;%=resultSet.getString(&quot;strasse&quot;) %&gt;&lt;/td&gt;
  52. 							&lt;td&gt;&lt;%=resultSet.getString(&quot;plz&quot;) %&gt;&lt;/td&gt;
  53. 							&lt;td&gt;&lt;%=resultSet.getString(&quot;ort&quot;) %&gt;&lt;/td&gt;
  54. 						&lt;/tr&gt;
  55. 						
  56. 						&lt;%
  57. 					}
  58. 					connection.close();
  59. 				}
  60. 				catch (Exception e) {
  61. 					e.printStackTrace();
  62. 				}
  63. 			%&gt;
  64. 			&lt;/table&gt;
  65.     &lt;/body&gt;
  66. &lt;/html&gt;

In the log-files i found two of the following error messages:

  1. An error occurred at line: [41] in the jsp file: [/index.jsp]
  2. userid cannot be resolved to a variable
  3. 38: 			
  4. 39: 			&lt;%
  5. 40: 				try{
  6. 41: 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  7. 42: 					statement=connection.createStatement();
  8. 43: 					String sql =&quot;select * from kunde&quot;;
  9. 44: 					resultSet = statement.executeQuery(sql);
  12. Stacktrace:] with root cause
  13. org.apache.jasper.JasperException: Unable to compile class for JSP: 
  15. An error occurred at line: [41] in the jsp file: [/index.jsp]
  16. userid cannot be resolved to a variable
  17. 38: 			
  18. 39: 			&lt;%
  19. 40: 				try{
  20. 41: 					connection = DriverManager.getConnection(connectionUrl+database, userid, password);
  21. 42: 					statement=connection.createStatement();
  22. 43: 					String sql =&quot;select * from kunde&quot;;
  23. 44: 					resultSet = statement.executeQuery(sql);

And

  1. [Warning] Access denied for user &#39;XY&#39;@&#39;localhost&#39; (using password: NO)

答案1

得分: 1

我解决了这个问题。
我需要将 mysql-connector-java-5.1.25-bin.jar 文件添加到我的 tomcat 的 lib 文件夹中。

英文:

I solved the problem.
I needed to add the mysql-connector-java-5.1.25-bin.jar file to my tomcat's lib.

huangapple
  • 本文由 发表于 2020年9月14日 23:52:18
  • 转载请务必保留本文链接：https://go.coder-hub.com/63887756.html
  • html
  • java
  • jsp
  • sql
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