我已经在.../ROOT/WEB-INF/lib
和Tomcat 8.0/lib
中放置了mysql驱动程序,但没有效果。我使用以下类连接到DB:
package db;
import java.sql.*;
public class ConnectToDB implements AutoCloseable {
Connection con;
public ConnectToDB(String server, String database, String user,
String password) throws SQLException {
con = DriverManager.getConnection("jdbc:mysql://" + server + "/"
+ database, user, password);
}
@Override
public void close() throws SQLException {
con.close();
}
public Connection getConnection() {
return con;
}
}
Eclipse项目中包含以下类:
1.src/nr3/model
package nr3.model;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import db.ConnectToDB;
public class MusikkHandler {
private ConnectToDB db;
private Connection con;
private String tableName;
private PreparedStatement pstmtGetRows;
public MusikkHandler(String server, String database, String user,
String password) throws SQLException {
db = new ConnectToDB(server, database, user, password);
con = db.getConnection();
tableName = "album";
}
public void close() throws SQLException {
db.close();
}
public ArrayList<Album> getRows(String genre) throws SQLException {
ArrayList<Album> list = new ArrayList<Album>();
pstmtGetRows = con.prepareStatement("SELECT * FROM " + tableName
+ " WHERE SJANGER = ?");
pstmtGetRows.setString(1, genre);
ResultSet rs = pstmtGetRows.executeQuery();
while (rs.next()) {
list.add(new Album(rs.getString(1), rs.getString(2), rs.getInt(3),
rs.getInt(4), rs.getString(5)));
}
rs.close();
pstmtGetRows.close();
return list;
}
}
-
package nr3.model;
public class Album {
private String tittel;
private String artist;
private int spor;
private int utgitt;
private String sjanger;
public Album (String artist, String tittel, int spor, int utgitt, String sjanger){
setArtist(artist);
setTittel(tittel);
setUtgitt(utgitt);
setSpor(spor);
setSjanger(sjanger);
}
public Album(){
this(null, null, 0, 0, null);
}
public void setTittel(String tittel){
this.tittel = tittel;
}
public void setArtist(String artist){
this.artist = artist;
}
public void setSpor(int spor) {
this.spor = spor;
}
public void setUtgitt(int utgitt) {
this.utgitt = utgitt;
}
public void setSjanger(String sjanger) {
this.sjanger = sjanger;
}
public String getTittel() {
return tittel;
}
public String getArtist() {
return artist;
}
public int getSpor() {
return spor;
}
public int getUtgitt() {
return utgitt;
}
public String getSjanger() {
return sjanger;
}
public String toString(){
return getTittel() + " (" + getArtist() + ")" + " Utgitt: "
+ getUtgitt();
}
}
2.src/nr3/servlets
package nr3.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import nr3.model.Album;
import nr3.model.MusikkHandler;
public class MusikkValg extends HttpServlet {
private static final long serialVersionUID = 428937262021570370L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String genre = request.getParameter("sjanger");
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
MusikkHandler mh;
out.println("<html>");
out.println("<head>");
out.println("<title>Musikk</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>MUSIKK-ANBEFALINGER</h1>");
out.println("<br/>");
out.println("<br/>");
out.println("<h3>Da bør du kanskje forsøke en av disse:</h3>");
out.println("<br/>");
out.println("<br/>");
try {
mh = new MusikkHandler(" ", " ", " ", " ");
for (Album a : mh.getRows(genre))
out.println("<p>" + a + "</p>");
} catch (SQLException e) {
e.printStackTrace(out);
}
out.println("</body>");
out.println("</html>");
}
}
更新:我在浏览器中收到以下错误stacktrace:
java.sql.SQLException:找不到适合的驱动程序jdbc:mysql://localhost/pg3100在位于的java.sql.DriverManager.getConnection(未知源)位于的java.sql.DriverManager.getConnection(未知源)数据库。ConnectToDB。(ConnectToDB.java:10)位于nr3.model.MusikHandler。(MusikkHandler。java:20)位于nr3.servlets.MusikkValg.doGet(MusikkValg.java:39)位于的javax.servlet.httpHttpServlet.service(HttpServlet.java:618)位于的javax.servlet.httpHttpServlet.service(HttpServlet.java:725)org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)在org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)在org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)在org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)在org.apache.catalina.core.StandardWrapperValv.invoke(StandardWrapperValve.java:219)在org.apache.catalina.core.StandardContextValv.invoke(StandardContextValv.java:106)在org.apache.catalina.authenticator.AuthenticatorBase.ioke(AuthenticatorBase.java:505)在org.apache.catalina.core.StandardHostValv.invoke(StandardHostValve.java:142)在org.apache.catalina.vals.ErrorReportValve.ioke(ErrorReportValve.java:79)在org.apache.catalina.vals.AbstractAccessLogValve.ioke(AbstractAccessLogValve.java:610)在org.apache.catalina.core.StandardEngineValv.invoke(StandardEngineValv.java:88)在org.apache.catalina.connecter.CoyoteAdapter.service(Coyotedapter.java:534)在org.apache.coyote.http11.AbstractHttp11Processor.procedure(AbstractHttp11Processer.java:1081)在org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)在org.apache.coyote.http11.Http11PrProtocol$Http11ConnectionHandler.process(Http11PrProtocol.java:277)在org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2381)在org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370)位于java.util.concurrent.ThreadPoolExecutor.runWorker(未知源)位于java.util.concurrent.ThreadPoolExecutor$Worker.run(未知源)在org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)在java.lang.Thread.run(未知源)
首先,您必须在开始时注册驱动程序,以便DriverManager在获得连接时可以使用它。它可能因实施而异。
DriverManager.registerDriver (new com.mysql.jdbc.Driver());
或
Class.forName("com.mysql.jdbc.Driver");
然后您可以执行getConnection()
,因为您将注册一个驱动程序供DriverManager使用。
第二:/webapps/ROOT/WEB-INF/lib
是一个不同的上下文,它的库将不可用于您的应用程序,除非您设置应用程序的上下文路径,如本问题所示。如果您想添加它,请先尝试将JDBC驱动程序放在/webapps/<yourapp>/lib
上。Tomcatlib应该也能正常工作(但当你分发应用程序时,它不太好,可能会与部署在那里的其他应用程序冲突,使用不同版本的驱动程序等)
第三:当在这里提问时,试着把你的可验证的例子简化为可读的。有很多代码与您的问题无关。减少会使阅读问题和提供帮助变得更容易。