我正在尝试使用我的 JSP 文件从 MySQL 数据库中检索值；但是，我收到以下错误:
java.math.BigInteger 不能转换为 java.lang.Long
MySQL数据库:
DROP DATABASE IF EXISTS cars;
CREATE DATABASE cars;
USE cars;
DROP TABLE IF EXISTS manufacturer;
CREATE TABLE manufacturer (
manufacturerID int NOT NULL AUTO_INCREMENT,
manufacturer varchar(30) NOT NULL,
PRIMARY KEY (manufacturerID)
);
INSERT INTO manufacturer (manufacturer) VALUES ('Nissan'),('Honda'),
('Ford'),('Hyundai'),('Volkswagen'),('Chevrolet');
JSP 文件:
<%@ page language="java" import="java.sql.*" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<% out.println("JSP Database");%>
<%!
Connection conn;
Statement stmt;
ResultSet rs;
%>
<table border="1">
<tr> <th>Manufacturer ID</th> <th>Manufacturer Name</th></tr>
<%
try{
String connectionUrl="jdbc:mysql://localhost:3306/cars";
String connectionUser="root";
String connectionPassword="admin";
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn=DriverManager.getConnection(connectionUrl, connectionUser, connectionPassword);
stmt=conn.createStatement();
rs=stmt.executeQuery("select * from manufacturer");
while(rs.next()) {
out.println(rs.getString("manufacturer")); %>
<tr>
<td> <% out.println(rs.getInt("manufacturerID")); %> </td>
<td> <%=rs.getString("manufacturer") %></td>
</tr>
<%
}
}
catch(Exception cnfex){
cnfex.printStackTrace();
}
finally{
if(rs!=null) rs.close();
if(stmt!=null) stmt.close();
if(conn!=null) conn.close();
}
%>
</table>
控制台:
java.sql.SQLException: java.lang.ClassCastException: java.math.BigInteger cannot be cast to java.lang.Long
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1078)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:920)
at com.mysql.jdbc.ConnectionImpl.buildCollationMapping(ConnectionImpl.java:1074)
at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3590)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2531)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2301)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at org.apache.jsp.JSPFile_jsp._jspService(JSPFile_jsp.java:141)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1374)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassCastException: java.math.BigInteger cannot be cast to java.lang.Long
at com.mysql.jdbc.ConnectionImpl.buildCollationMapping(ConnectionImpl.java:1019)
... 43 more
我为解决问题所做的工作:
- 我已将 sql jar 文件从构建路径移动到 Web 内容下的 lib 文件夹
- 在 friend 的电脑上运行这个项目(它运行得非常好!)
- 重新安装 eclipse
我知道这不是使用 JDBC 或 JSP 的推荐方式。这是在类里面完成的一个示例，它适用于除我以外的所有人。我在尝试使用 Servlet 从数据库中检索数据时也遇到了同样的问题。
感谢任何有关如何解决此问题的帮助。提前致谢!
最佳答案
我考虑到您能够连接到数据库，唯一的问题是关于获取制造商 ID。
试试这个 ((BigInteger)rs.getInt("manufacturerID")).intValue()
关于java - 我无法使用 JSP 文件从 MySQL 数据库检索数据并收到 java.math.BigInteger cannot be cast to java.lang.Long 错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47799066/