用jdbc连接数据库并简单执行SQL语句
Posted 南山南
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了用jdbc连接数据库并简单执行SQL语句相关的知识，希望对你有一定的参考价值。
一：版本一.这种存在一个问题就是每执行一次操作都会创建一次Connection链接和且释放一次链接
1：创建pojo对象（OR映射，一个pojo类对应一张数据库表）
1 package com.yinfu.dao; 2 3 public class Employee { 4 5 private int id; 6 private String name; 7 private String password; 8 public int getId() { 9 return id; 10 } 11 public void setId(int id) { 12 this.id = id; 13 } 14 public String getName() { 15 return name; 16 } 17 public void setName(String name) { 18 this.name = name; 19 } 20 public String getPassword() { 21 return password; 22 } 23 public void setPassword(String password) { 24 this.password = password; 25 } 26 @Override 27 public String toString() { 28 return "Employee [id=" + id + ", name=" + name + ", password=" + password + "]"; 29 } 30 public Employee(int id, String name, String password) { 31 super(); 32 this.id = id; 33 this.name = name; 34 this.password = password; 35 } 36 public Employee() { 37 super(); 38 } 39 }
2：创建数据库连接用的数据文件，用于外界读取数据(properties文件)：
1 driver=com.mysql.jdbc.Driver 2 jdbcUrl=jdbc:mysql://localhost:3306/test 3 user=root 4 password=song12345
3：创建数据库连接和关闭连接的工具类(被重复使用的方法可以写在工具类中)：
1 package com.yinfu.utils; 2 3 import java.io.IOException; 4 import java.io.InputStream; 5 import java.sql.Connection; 6 import java.sql.DriverManager; 7 import java.sql.PreparedStatement; 8 import java.sql.ResultSet; 9 import java.sql.SQLException; 10 import java.util.Properties; 11 /** 12 * JDBC的工具类，封装了jdbc的一些方法 13 * @author lusong 14 * 15 */ 16 public class JDBCUtils { 17 18 //关闭jdbc的链接 19 /** 20 * 关闭statement和connection 21 * @param ps 22 * @param conn 23 */ 24 public static void release(PreparedStatement ps, Connection conn){ 25 try { 26 if(ps != null){ 27 ps.close(); 28 } 29 } catch (SQLException e) { 30 e.printStackTrace(); 31 }finally{ 32 try { 33 if(conn != null){ 34 conn.close(); 35 } 36 } catch (SQLException e) { 37 e.printStackTrace(); 38 } 39 } 40 } 41 public static void release(ResultSet result,PreparedStatement ps, Connection conn){ 42 try { 43 if(result != null){ 44 result.close(); 45 } 46 } catch (SQLException e1) { 47 e1.printStackTrace(); 48 }finally{ 49 try { 50 if(ps != null){ 51 ps.close(); 52 } 53 } catch (SQLException e) { 54 e.printStackTrace(); 55 }finally{ 56 try { 57 if(conn != null){ 58 conn.close(); 59 } 60 } catch (SQLException e) { 61 e.printStackTrace(); 62 } 63 } 64 } 65 66 } 67 68 //获取jdbc的链接 69 /** 70 * 用于创建jdbc链接的工具类对象 71 * @return 72 */ 73 public static Connection getConnetions() { 74 Connection conn = null; 75 String driverClass = null; 76 String jdbcUrl = null; 77 String user = null; 78 String password = null; 79 80 try { 81 //读取配置文件中的配置 82 InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("db.properties"); 83 Properties properties = new Properties(); 84 properties.load(is); 85 driverClass = properties.getProperty("driver"); 86 jdbcUrl = properties.getProperty("jdbcUrl"); 87 user = properties.getProperty("user"); 88 password = properties.getProperty("password"); 89 //注册驱动程序 90 Class.forName(driverClass); 91 //实际应该这样写(由于对应的应用程序中有一个对应的静态代码块，自动回将驱动的类对象进行驱动加载) 92 //DriverManager.registerDriver((Driver) Class.forName(driverClass).newInstance()); 93 94 conn = DriverManager.getConnection(jdbcUrl,user,password); 95 96 } catch (IOException e) { 97 // TODO Auto-generated catch block 98 e.printStackTrace(); 99 }catch (SQLException e) { 100 // TODO Auto-generated catch block 101 e.printStackTrace(); 102 }catch (ClassNotFoundException e) { 103 // TODO Auto-generated catch block 104 e.printStackTrace(); 105 } 106 return conn; 107 } 108 }
4：用Junit测试实现的JDBC实现数据库的增删改查操作：
1 package com.yinfu.test; 2 3 import java.io.IOException; 4 import java.io.InputStream; 5 import java.sql.Connection; 6 import java.sql.DriverManager; 7 import java.sql.PreparedStatement; 8 import java.sql.ResultSet; 9 import java.sql.SQLException; 10 import java.util.ArrayList; 11 import java.util.List; 12 import java.util.Properties; 13 14 import org.junit.Test; 15 16 import com.yinfu.dao.Employee; 17 import com.yinfu.utils.JDBCUtils; 18 19 public class JDBCTest { 20 21 @Test 22 public void testUpdate(){ 23 //曾 24 String sql = "insert into employee (Id,Name,Password) values (1,‘wangba‘,131)"; 25 //删 26 //String sql = "delete from employee where id = 1"; 27 //改 28 //String sql = "update employee set name = ‘fuck‘ where id = 2"; 29 //查 30 String sqlQuery = "select * from employee"; 31 update(sql); 32 testQueryObject(sqlQuery); 33 } 34 35 public void testQueryObject(String sql){ 36 Employee employee = null; 37 List<Employee> list = new ArrayList(); 38 Connection conn = null; 39 PreparedStatement ps = null; 40 ResultSet result = null; 41 try { 42 //创建连接 43 conn = JDBCUtils.getConnetions(); 44 //创建prepareStatement对象，用于执行SQL 45 ps = conn.prepareStatement(sql); 46 //获取查询结果集 47 result = ps.executeQuery(); 48 while(result.next()){ 49 employee = new Employee(result.getInt(1),result.getString(2),result.getString(3)); 50 list.add(employee); 51 } 52 System.out.println(list); 53 } catch (Exception e) { 54 e.printStackTrace(); 55 }finally{ 56 JDBCUtils.release(result, ps, conn); 57 } 58 } 59 60 public void update(String sql){ 61 Connection conn = null; 62 PreparedStatement ps = null; 63 try { 64 //创建数据库连接 65 conn = JDBCUtils.getConnetions(); 66 //创建执行SQL的prepareStatement对象 67 ps = conn.prepareStatement(sql); 68 //用于增删改操作 69 int result = ps.executeUpdate(); 70 System.out.println(result); 71 } catch (Exception e) { 72 System.out.println("出现异常1="+e.toString()); 73 }finally{ 74 JDBCUtils.release(ps, conn); 75 } 76 77 78 } 79 }
以上是关于用jdbc连接数据库并简单执行SQL语句的主要内容，如果未能解决你的问题，请参考以下文章