Question

我正在尝试使用Microsoft SQL Server的jdbc驱动程序连接到我的数据库，但我设法与服务器建立了连接，但是发生了一些奇怪的事情。这是我的Dconnector类：

package com.myblog;
import com.microsoft.sqlserver.jdbc.SQLServerDriver;
import java.sql.*;
import java.util.Properties;

public class Dconnector {
public Connection connection = null;
public Statement stmt;
static Properties prop = null;
public Dconnector() throws SQLException {
    DriverManager.registerDriver(new SQLServerDriver());
    System.out.println("SQL JDBC Connection Testing");
    prop = new Properties();
    try {
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        String DB_CONN_STRING = "jdbc:sqlserver://localhost:1434;databaseName=blogdb;";
        //Provided by your driver documentation. In this case, a MySql driver is used :
        String USER_NAME = "sa";
        String PASSWORD = "pwd";
        connection =DriverManager.getConnection(DB_CONN_STRING, USER_NAME, PASSWORD);
        stmt = connection.createStatement();
    } catch (SQLException e) {
        System.out.println("Connection Failed! Check output console");
        e.printStackTrace();

    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }


    if (connection != null) {
        System.out.println("Connected!");
    } else {
        System.out.println("Failed to connect!");
    }

}

public ResultSet queryResult(String Query) {
    ResultSet rst = null;
    try {
        rst = stmt.executeQuery(Query);
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return rst;
}

public int queryCount(String Query) {
    int count = 0;
    try {
        count = stmt.executeUpdate(Query);
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return count;
}
public void closeConnection()
{
    try {
        connection.close();
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
   }
}

奇怪的是，当我启动Web应用并像下面这样创建Dconnector的新实例时：

com.myblog.Dconnector db=new com.myblog.Dconnector();

并使用以下命令将其关闭：

db.closeConnection();

由于某种原因，该班级似乎被低估了3次？在控制台中，依次单击“ SQL JDBC连接测试”和“已连接！”。显示3次。

此外，当我尝试在连接打开与关闭之间的任何查询中调用queryResult时，所有内容都将中断，并且读取预登录响应时出错，并且连接重置再次重复3次。

这是.jsp文件（脚本）中使用的代码：

com.myblog.Dconnector db=new com.myblog.Dconnector();
  ResultSet rst=db.queryResult("SELECT Caption FROM ArticlesTB");
    ResultSetMetaData rsmd = rst.getMetaData();
    int columnsNumber = rsmd.getColumnCount();
  try {
      while (rst.next()) {
          for (int i = 1; i <= columnsNumber; i++) {
              String columnValue = rst.getString(i);
              System.out.print("<h1>" +columnValue + " 
    </h1>"+System.getProperty("line.separator"));
          }


  }}
  catch (SQLException e)
  {
      e.printStackTrace();
      System.out.println("This did not work");
  }

db.closeConnection();

我现在只是输出到控制台进行测试。控制台输出的相关部分如下：

Connected to server
[2018-09-05 11:53:39,507] Artifact Stranka:war exploded: Artifact is being 
deployed, please wait...
05-Sep-2018 23:53:40.372 INFO [RMI TCP Connection(3)-127.0.0.1] 
org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned 
for TLDs yet contained no TLDs. Enable debug logging for this logger for a 
complete list of JARs that were scanned but no TLDs were found in them. 
Skipping unneeded JARs during scanning can improve startup time and JSP 
compilation time.
[2018-09-05 11:53:40,435] Artifact Stranka:war exploded: Artifact is deployed 
successfully
[2018-09-05 11:53:40,435] Artifact Stranka:war exploded: Deploy took 928 
milliseconds
-------- SQL JDBC Connection Testing ------------
You made it, take control your database now!
(h1)This is a sample article(/h1)
(h1)This is a second article.(/h1)
(h1)This is a third sample.(/h1)
-------- SQL JDBC Connection Testing ------------
You made it, take control your database now!
(h1)This is a sample article(/h1)
(h1)This is a second article.(/h1)
(h1)This is a third sample.(/h1)
-------- SQL JDBC Connection Testing ------------
You made it, take control your database now!
(h1)This is a sample article(/h1)
(h1)This is a second article.(/h1)
(h1)This is a third sample.(/h1)
05-Sep-2018 23:53:49.219 INFO 
[ContainerBackgroundProcessor[StandardEngine[Catalina]]] 
org.apache.catalina.startup.HostConfig.deployDirectory Deploying web 
application directory [C:\apache-tomcat-9.0.11\webapps\manager]
05-Sep-2018 23:53:49.312 INFO 
[ContainerBackgroundProcessor[StandardEngine[Catalina]]] 
org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web 
application directory [C:\apache-tomcat-9.0.11\webapps\manager] has finished 
in [93] ms

已编辑HTML标记以保持代码格式。

JDBC连接问题

0 个答案: