JDBC的使用流程

Posted 2020-09-08 corolcorona

导入包:

import java.sql.*;

 

注册JDBC驱动程序：

Class.forName("com.mysql.jdbc.Driver");

 

打开一个连接：

conn = DriverManager.getConnection(DB_URL,USER,PASS);

 

执行一个查询

stmt = conn.createStatement();

String sql;

sql = "SELECT id, first, last, age FROM Employees";

ResultSet rs = stmt.executeQuery(sql);

 

sql = "DELETE FROM Employees";

ResultSet rs = stmt.executeUpdate(sql);

 

从结果集中提取数据：

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");

        

清理环境：    

rs.close();

stmt.close();

conn.close();

 

//STEP 1. Import required packages

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/EMP";

 

   //  Database credentials

   static final String USER = "username";

   static final String PASS = "password";

  

   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, first, last, age FROM Employees";

      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();

   }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 - by www.yiibai.com