Java 连接sql server 2012，第一次成功，换了工程报错 class.forName

[zhangwenqing123]

千辛万苦地在win10环境下，给Java用jdbc连接数据库sql server2012

先用一个小项目测试成功了，换回正宫项目就连不上了不造为什么。求大神解答。。。

package pkg;

import java.sql.*;
//import java.sql.DriverManager;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		 String driverName="com.microsoft.sqlserver.jdbc.SQLServerDriver";

		  String dbURL="jdbc:sqlserver://localhost:49420;DatabaseName=Test";

		  String userName="zwq";

		  String userPwd="qwe123456";

		  try

		  {

		   Class.forName(driverName);

		   Connection dbConn=DriverManager.getConnection(dbURL,userName,userPwd);

		    System.out.println("连接数据库成功");
		    
		    try{
		    dbConn.close();
		    System.out.println("断开数据库成功");
		    }catch(Exception e){
		    	System.out.println("断开数据库失败");
		    }
		  }

		  catch(Exception e)

		  {

		   e.printStackTrace();

		   System.out.print("连接失败");

		  }    	
		  //rs.close();
	      //stmt.close();
		  
	}

}

编译结果是
连接数据库成功
断开数据库成功

于是测试成功后就用我的项目连接数据库，然后报错。。。
以下是代码

package edition1;
import java.sql.*;
import java.math.*;
import java.lang.*;

public class Main {
	// JDBC driver name and database URL
	   static final String JDBC_DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";  
	   static final String DB_URL = "jdbc:sqlserver://localhost:49420;DatabaseName=Test";

	   //  Database credentials
	   static final String USER = "zwq";
	   static final String PASS = "qwe123456";

	   public static void main(String[] args) {
		   /*String PASS = "qwe123456";
		   String USER = "zwq";
		   String JDBC_DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
		   String DB_URL = "jdbc:sqlserver://localhost:49420;DatabaseName=TestJdbc";*/
	   Connection conn = null;
	   Statement stmt = null;
	   try{
	      //STEP 2: Register JDBC driver
		   try{
	      Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
		   
		   }catch(Exception e){
			   e.printStackTrace();
			   System.out.println("Class.forName错误");
		   }
	      //STEP 3: Open a connection
	      System.out.println("Connecting to database...");
	      try{
	    	  conn = DriverManager.getConnection(DB_URL,USER,PASS);
	      }catch(Exception e){
	    	  e.printStackTrace();
	    	  System.out.println("conn错误");
	      }
	      

	      //STEP 4: Execute a query
	      System.out.println("Creating statement...");
	      stmt = conn.createStatement();
	      String sql;
	      sql = "SELECT bookId FROM DHB";
	      ResultSet rs = stmt.executeQuery(sql);

	      //STEP 5: Extract data from result set
	      while(rs.next()){
	         //Retrieve by column name
	         int id  = rs.getInt("id");
	         //int age = rs.getInt("age");
	         //String first = rs.getString("first");
	         //String last = rs.getString("last");

	         //Display values
	         System.out.print("ID: " + id);
	         /*System.out.print(", Age: " + age);
	         System.out.print(", First: " + first);
	         System.out.println(", Last: " + last);*/
	      }
	      //STEP 6: Clean-up environment
	      rs.close();
	      stmt.close();
	      conn.close();
	   }catch(SQLException se){
	      //Handle errors for JDBC
	      se.printStackTrace();
		   System.out.println("JDBC捕捉");
	   }catch(Exception e){
	      //Handle errors for Class.forName
	      e.printStackTrace();
		   System.out.println("class.forname捕捉");
	   }finally{
	      //finally block used to close resources
	      try{
	         if(stmt!=null)
	            stmt.close();
	      }catch(SQLException se2){
	      }// nothing we can do
	      try{
	         if(conn!=null)
	            conn.close();
	      }catch(SQLException se){
	         se.printStackTrace();
	      }//end finally try
	   }//end try
	   System.out.println("Goodbye!");
	}//end main

}//end FirstExample

编译结果是
java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at edition1.Main.main(Main.java:25)
Class.forName错误
Connecting to database...
java.sql.SQLException: No suitable driver found for jdbc:sqlserver://localhost:49420;DatabaseName=Test
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at edition1.Main.main(Main.java:34)
conn错误
Creating statement...
java.lang.NullPointerException
at edition1.Main.main(Main.java:43)
class.forname捕捉
Goodbye!

[shoppo0505]

DatabaseName=TestJdbc？？？

[水蓝淡影]

会不会是工程名有错误，或者是database 的名字没有写正确？我看一个Test，一个是TestJdbc。