Java 在eclipse中将Servlet连接到MySQL数据库
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Connect Servlet to MySQL database in eclipse
提问by Pushpendra
I successfully connected database with simple java program using JDBC but when I am trying to connect database with Servlet, it gives me following errors and exceptions:
我使用 JDBC 成功地将数据库与简单的 java 程序连接起来，但是当我尝试将数据库与 Servlet 连接时，它给了我以下错误和异常：
java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:8888/ebookshop
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at QueryServlet.doGet(QueryServlet.java:35)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:534)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
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)
All severs running well and also I already added servlet and connecter API's in my library.
所有服务器都运行良好，而且我已经在我的库中添加了 servlet 和连接器 API。
For more Information these are my html and servlet files are:
有关更多信息，这些是我的 html 和 servlet 文件是：
html file
html文件
<html>
<head><title>Yet Another Bookshop</title></head>
<body>
<h2>Yet Another Bookshop</h2>
<form method="get" action="http://localhost:9999/Sixth/query">
<b>Choose an author:</b>
<input type="checkbox" name="author" value="Tan Ah Teck">Ah Teck
<input type="checkbox" name="author" value="Mohammad Ali">Ali
<input type="checkbox" name="author" value="Kumar">Kumar
<input type="submit" value="Search">
</form>
</body>
</html>
My servlet:
我的 servlet：
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class QueryServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
// JDK 6 and above only
// The doGet() runs once per HTTP GET request to this servlet.
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// Set the MIME type for the response message
response.setContentType("text/html");
// Get a output writer to write the response message into the network socket
PrintWriter out = response.getWriter();
Connection conn = null;
Statement stmt = null;
try {
// Step 1: Allocate a database Connection object
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(
"jdbc:mysql://localhost:8888/ebookshop", "myuser", "xxxx"); // <== Check!
// database-URL(hostname, port, default database), username, password
// Step 2: Allocate a Statement object within the Connection
stmt = conn.createStatement();
// Step 3: Execute a SQL SELECT query
String sqlStr = "select * from books where author = "
+ "'" + request.getParameter("author") + "'"
+ " and qty > 0 order by price desc";
// Print an HTML page as the output of the query
out.println("<html><head><title>Query Response</title></head><body>");
out.println("<h3>Thank you for your query.</h3>");
out.println("<p>You query is: " + sqlStr + "</p>"); // Echo for debugging
ResultSet rset = stmt.executeQuery(sqlStr); // Send the query to the server
// Step 4: Process the query result set
int count = 0;
while (rset.next()) {
// Print a paragraph <p>...</p> for each record
out.println("<p>" + rset.getString("author")
+ ", " + rset.getString("title")
+ ", $" + rset.getDouble("price") + "</p>");
count++;
}
out.println("<p>==== " + count + " records found =====</p>");
out.println("</body></html>");
} catch (SQLException ex) {
ex.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
回答by Santhosh
you should add this line,
你应该添加这一行，
Class.forName("com.mysql.jdbc.Driver");
As it is the first step to establish connection with JDBCdriver,
由于这是与JDBC驱动程序建立连接的第一步，
Connection conn = null;
Statement stmt = null;
try {
Class.forName("com.mysql.jdbc.Driver");
// Step 1: Allocate a database Connection object
conn = DriverManager.getConnection(
"jdbc:mysql://localhost:8888/ebookshop", "myuser", "xxxx"); // <== Check!
// database-URL(hostname, port, default database), username, password
// Step 2: Allocate a Statement object within the Connection
stmt = conn.createStatement();
Provide that you added the mysql connectorjar in your buidpath
提供您mysql connector在 buidpath 中添加的jar
回答by Bruno Franco
You need to load your driver before you get a connection, something like that:
您需要在获得连接之前加载驱动程序，如下所示：
//Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
Here is a nice example: http://www.tutorialspoint.com/jdbc/jdbc-sample-code.htm
这是一个很好的例子：http: //www.tutorialspoint.com/jdbc/jdbc-sample-code.htm
回答by SparkOn
As I see this jdbc:mysql://localhost:8888/ebookshopyou have changed the default port of mysql from 3306to 8888
正如我所看到的，jdbc:mysql://localhost:8888/ebookshop您已将 mysql 的默认端口从 更改3306为8888
If you did not change the port just use 3306 as the port for mysql
如果您没有更改端口，请使用 3306 作为 mysql 的端口
As the exception is saying No suitable driver foundthat obviously means you don't have the
mysql-connector-[version].jarin your classpath If you are using eclipse just place the jar under WEB-INF/liband if you are using standalone tomcat just place the driver jar in the lib folder of Tomcat
作为例外No suitable driver found，这显然意味着您的类路径中没有
mysql-connector-[version].jar如果您使用的是 eclipse，只需将 jar 放在下面WEB-INF/lib，如果您使用的是独立的 tomcat，只需将驱动程序 jar 放在Tomcat的lib文件夹
回答by Prasad De Silva
try this
尝试这个
public static void connect() throws Exception {
Class.forName("com.mysql.jdbc.Driver").newInstance();
String url = "jdbc:mysql://localhost:3306/database_name?autoReconnect=true";
c = DriverManager.getConnection(url,"root","123");
}
thanx..
谢谢..
