Java MySql数据库访问JDBC驱动程序

它总是返回错误页面

 public String execute()  
 {
      String ret = ERROR;
      Connection conn = null;

      try {
           String URL = "jdbc:mysql://localhost/code";
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(URL, "root", "mysql");
           String sql = "SELECT username FROM user WHERE";
           sql+=" username = ? AND password = ?";
           PreparedStatement ps = conn.prepareStatement(sql);
           ps.setString(1, username);
           ps.setString(2, password);
           ResultSet rs = ps.executeQuery();

           while (rs.next()) {
               name = rs.getString(1);
               ret = SUCCESS;
           }
     } catch (Exception e) {
           ret = ERROR;
     } 
     finally {
           if (conn != null) {
               try {
                   conn.close();
               }
               catch (Exception e){}
            }
     }
     return ret;
 }

类文件以访问Struts2中的数据库。我的数据库用户名：root，密码：mysql数据库名为“code”，表名为“user”

 public String execute()  
 {
      String ret = ERROR;
      Connection conn = null;

      try {
           String URL = "jdbc:mysql://localhost/code";
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(URL, "root", "mysql");
           String sql = "SELECT username FROM user WHERE";
           sql+=" username = ? AND password = ?";
           PreparedStatement ps = conn.prepareStatement(sql);
           ps.setString(1, username);
           ps.setString(2, password);
           ResultSet rs = ps.executeQuery();

           while (rs.next()) {
               name = rs.getString(1);
               ret = SUCCESS;
           }
     } catch (Exception e) {
           ret = ERROR;
     } 
     finally {
           if (conn != null) {
               try {
                   conn.close();
               }
               catch (Exception e){}
            }
     }
     return ret;
 }

这是我的struts.xml

 public String execute()  
 {
      String ret = ERROR;
      Connection conn = null;

      try {
           String URL = "jdbc:mysql://localhost/code";
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(URL, "root", "mysql");
           String sql = "SELECT username FROM user WHERE";
           sql+=" username = ? AND password = ?";
           PreparedStatement ps = conn.prepareStatement(sql);
           ps.setString(1, username);
           ps.setString(2, password);
           ResultSet rs = ps.executeQuery();

           while (rs.next()) {
               name = rs.getString(1);
               ret = SUCCESS;
           }
     } catch (Exception e) {
           ret = ERROR;
     } 
     finally {
           if (conn != null) {
               try {
                   conn.close();
               }
               catch (Exception e){}
            }
     }
     return ret;
 }

<struts>
    <constant name="struts.devMode" value="true" />
    <package name="com.code" extends="struts-default">
        <action name="loginaction" class="com.code.Login"  method="execute">
           <result name="success">/Login.jsp</result>
           <result name="error">/error.jsp</result>
        </action>   
    </package>
</struts>

/Login.jsp
/error.jsp

为什么这不是返回成功页面？

您的数据库url中缺少数据库的端口号

 public String execute()  
 {
      String ret = ERROR;
      Connection conn = null;

      try {
           String URL = "jdbc:mysql://localhost/code";
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(URL, "root", "mysql");
           String sql = "SELECT username FROM user WHERE";
           sql+=" username = ? AND password = ?";
           PreparedStatement ps = conn.prepareStatement(sql);
           ps.setString(1, username);
           ps.setString(2, password);
           ResultSet rs = ps.executeQuery();

           while (rs.next()) {
               name = rs.getString(1);
               ret = SUCCESS;
           }
     } catch (Exception e) {
           ret = ERROR;
     } 
     finally {
           if (conn != null) {
               try {
                   conn.close();
               }
               catch (Exception e){}
            }
     }
     return ret;
 }

如果您使用的是MySql，默认端口号为

3306

。尝试更改url，如下所示：

 public String execute()  
 {
      String ret = ERROR;
      Connection conn = null;

      try {
           String URL = "jdbc:mysql://localhost/code";
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(URL, "root", "mysql");
           String sql = "SELECT username FROM user WHERE";
           sql+=" username = ? AND password = ?";
           PreparedStatement ps = conn.prepareStatement(sql);
           ps.setString(1, username);
           ps.setString(2, password);
           ResultSet rs = ps.executeQuery();

           while (rs.next()) {
               name = rs.getString(1);
               ret = SUCCESS;
           }
     } catch (Exception e) {
           ret = ERROR;
     } 
     finally {
           if (conn != null) {
               try {
                   conn.close();
               }
               catch (Exception e){}
            }
     }
     return ret;
 }

String URL = "jdbc:mysql://localhost:3306/code";

---

谢谢你的回复。我更改了我的端口号。但没有任何更改。发生了相同的错误。请打印堆栈跟踪并检查生成的错误。修改此行

}catch（异常e）{ret=error；}

使用`}catch（异常e）{ret=error；e.printStackTrace（）；}”“谢谢，但它也不打印任何例外。