public class UserDao {
public static boolean login(User loginUser) throws SQLException {
//1.撰寫sql
String sql = "select * from user where username=? and password=?";
//2.獲取連接連接資料庫
Connection conn = JDBCUtils.getConnection();
PreparedStatement pps = conn.prepareStatement(sql);
String usernmae = loginUser.getUsernmae();
String password = loginUser.getPassword();
pps.setString(1,usernmae);
pps.setString(2,password);
ResultSet resultSet = pps.executeQuery();
//如果回傳的視圖為空，則說明里面沒有這個賬號密碼
JDBCUtils.close(conn, (Statement) pps,resultSet);
if (resultSet==null){
return false;
}else {
return true;
}
}
}
uj5u.com熱心網友回復：
這是我測驗能否連接資料庫，但是顯示的是可以連接
public class UserDaoTest {
@Test
public void loginTest() {
User user = new User("123","123");
try {
boolean login = UserDao.login(user);
System.out.println(login);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
uj5u.com熱心網友回復：
當我使用服務器端時出現另一個問題，我把封裝的User物件user放進去這個UserDao.login（user）時就報錯@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//轉換編碼格式
request.setCharacterEncoding("utf-8");
//獲取請求資訊
Map<String, String[]> pm = request.getParameterMap();
//將其封裝為User物件
User user = new User();
Set<String> set = pm.keySet();
if (set!=null){
for (String s : set) {
String[] value = pm.get(s);
//根據key的值來傳遞，賬號密碼
if (s.equals("username")){
user.setUsernmae(value[0]);
}if(s.equals("password")){
user.setPassword(value[0]);
}
}
}
//判斷這個賬號是否存在
boolean login = false;
try {
login = UserDao.login(user);
} catch (SQLException e) {
e.printStackTrace();
}
if (login == true){
response.getWriter().write("登陸成功");
}else {
response.sendRedirect("/xgfirst/login.jsp");
}
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
uj5u.com熱心網友回復：
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1358)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1180)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:292)
at com.utils.JDBCUtils.<clinit>(JDBCUtils.java:25)
at com.userDao.UserDao.login(UserDao.java:20)
at com.servlet.LoginServlet.doPost(LoginServlet.java:45)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
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:52)
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:543)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:688)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:609)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1623)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Thread.java:844)
java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/mydb2
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:703)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:229)
at com.utils.JDBCUtils.getConnection(JDBCUtils.java:37)
at com.userDao.UserDao.login(UserDao.java:20)
at com.servlet.LoginServlet.doPost(LoginServlet.java:45)
uj5u.com熱心網友回復：
可能是mysql的jar包版本問題，如果你用的是hibernate的話，也可能是hibernate的版本問題，mysql的驅動jar包要跟你的mysql版本匹配uj5u.com熱心網友回復：
問題已經解決啦轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/108907.html
標籤：Java EE