如何在制作jdbc简单程序时删除此错误

Question

你好 我正在制作从数据库中获取数据的简单程序。我下载sql for mac并插入模式，然后是表和条目。所以我需要从数据库中检索数据。我正在使用mysql。 我还插入了mysql的conector jar。 我喜欢那样 import java.sql。*;

![public class FirstExample {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/Database";

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

   public static void main(String\[\] args) {
   Connection conn = null;
   Statement stmt = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);

      //STEP 4: Execute a query
      System.out.println("Creating statement...");
      stmt = conn.createStatement();
      String sql;
      sql = "SELECT id, name, age FROM Employee";
      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("name");
        // 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();
   }catch(Exception e){
      //Handle errors for Class.forName
      e.printStackTrace();
   }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][3]





Connecting to database...
Goodbye!
java.sql.SQLException: null,  message from server: "Host '192.168.1.100' is not allowed to connect to this MySQL server"
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1086)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1114)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2493)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2526)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2311)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347)
    at java.sql.DriverManager.getConnection(DriverManager.java:582)
    at java.sql.DriverManager.getConnection(DriverManager.java:185)
    at FirstExample.main(FirstExample.java:21)

Answer 1

您的数据库用户不允许连接到您的MySQL服务器。在MySQL中（奇怪的是）有类似防火墙的东西，每个主机每个用户定义访问权限。您需要通过任何SQL客户端连接到MySQL并提供访问权限：

http://dev.mysql.com/doc/refman/5.1/en/adding-users.html

例如，访问过于宽泛但应该有效：

GRANT ALL PRIVILEGES ON *.* TO 'monty'@'%' WITH GRANT OPTION;

如果您没有先创建用户：

CREATE USER 'monty'@'localhost' IDENTIFIED BY 'some_pass';