JDBC对数据库数据进行增删改查

Posted 2021-02-27 yxfyg

  1 package com.yxfyg.crud;
  2 
  3 import java.sql.Connection;
  4 import java.sql.ResultSet;
  5 import java.sql.SQLException;
  6 import java.sql.Statement;
  7 
  8 import org.junit.jupiter.api.Test;
  9 
 10 import com.yxfyg.util.JDBCUtil;
 11 
 12 public class TestCrud {
 13     
 14     @Test
 15     public void testQuery() {
 16         Connection conn = null;
 17         Statement st = null;
 18         ResultSet rs = null;
 19         try {
 20             conn = JDBCUtil.getConn();
 21             st = conn.createStatement();
 22             String sql = "select * from student";
 23             rs = st.executeQuery(sql);
 24             while(rs.next()) {
 25                 int sno = rs.getInt("sno");
 26                 String sname = rs.getString("sname");
 27                 String sex = rs.getString("ssex");
 28                 int sage = rs.getInt("sage");
 29                 String sdept = rs.getString("sdept");
 30                 System.out.println("sno="+ sno +",sname="+ sname +",sex="+ sex +",age="+ sage +",sdept=" + sdept);
 31             }
 32         } catch (SQLException e) {
 33             e.printStackTrace();
 34         } finally {
 35             JDBCUtil.release(rs, st, conn);
 36         }
 37     }
 38     
 39     @Test
 40     public void testInsert() {
 41         Connection conn = null;
 42         Statement st = null;
 43         try {
 44             conn = JDBCUtil.getConn();
 45             st = conn.createStatement();
 46             String sql = "insert into student values(null,‘刘文‘,‘男‘,20,‘MA‘)";
 47             //返回修改的行数
 48             int result = st.executeUpdate(sql);
 49             if(result > 0) {
 50                 System.out.println("添加成功");
 51             }else {
 52                 System.out.println("添加失败");
 53             }
 54         } catch (SQLException e) {
 55             e.printStackTrace();
 56         } finally {
 57             JDBCUtil.release(st, conn);
 58         }
 59     }
 60     
 61     @Test
 62     public void testUpdate() {
 63         Connection conn = null;
 64         Statement st = null;
 65         try {
 66             conn = JDBCUtil.getConn();
 67             st = conn.createStatement();
 68             String sql = "update student set sname = ‘测试‘ where sno = 5";
 69             //返回修改的行数
 70             int result = st.executeUpdate(sql);
 71             if(result > 0) {
 72                 System.out.println("更新成功");
 73             }else {
 74                 System.out.println("更新失败");
 75             }
 76         } catch (SQLException e) {
 77             e.printStackTrace();
 78         } finally {
 79             JDBCUtil.release(st, conn);
 80         }
 81     }
 82     
 83     @Test
 84     public void testDelete() {
 85         Connection conn = null;
 86         Statement st = null;
 87         try {
 88             conn = JDBCUtil.getConn();
 89             st = conn.createStatement();
 90             String sql = "delete from student where sno = 5";
 91             //返回修改的行数
 92             int result = st.executeUpdate(sql);
 93             if(result > 0) {
 94                 System.out.println("删除成功");
 95             }else {
 96                 System.out.println("删除失败");
 97             }
 98         } catch (SQLException e) {
 99             e.printStackTrace();
100         } finally {
101             JDBCUtil.release(st, conn);
102         }
103     }
104 }

 1 package com.yxfyg.util;
 2 
 3 import java.io.FileInputStream;
 4 import java.io.IOException;
 5 import java.io.InputStream;
 6 import java.sql.Connection;
 7 import java.sql.DriverManager;
 8 import java.sql.ResultSet;
 9 import java.sql.SQLException;
10 import java.sql.Statement;
11 import java.util.Properties;
12 
13 public class JDBCUtil {
14     
15     static String url = null;
16     static String driverClass = null;
17     
18     static {
19         try {
20             //1.创建一个属性配置对象
21             Properties properties = new Properties();
22             //2.使用类加载器去读取src底下的资源文件
23             InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
24             //若使用下面这种，properties文件要位于工程根目录
25             //InputStream is = new FileInputStream("jdbc.properties");
26             //3.导入输入流
27             properties.load(is);
28             //4.读取属性
29             driverClass = properties.getProperty("driverClass");
30             url = properties.getProperty("url");
31         } catch (IOException e) {
32             e.printStackTrace();
33         }
34     }
35     
36     public static void release(ResultSet rs,Statement st,Connection conn) {
37         closeRs(rs);
38         closeSt(st);
39         closeConn(conn);
40     }
41     
42     public static void release(Statement st,Connection conn) {
43         closeSt(st);
44         closeConn(conn);
45     }
46     
47     public static Connection getConn() {
48         Connection conn = null;
49         try {
50             Class.forName(driverClass);
51             conn = DriverManager.getConnection(url);
52         } catch (Exception e) {
53             e.printStackTrace();
54         }
55         return conn;
56     }
57     
58     private static void closeRs(ResultSet rs) {
59         try {
60             if(rs != null) {
61                 rs.close();
62             }
63         }catch(SQLException e) {
64             e.printStackTrace();
65         }finally {
66             rs = null;
67         }
68     }
69     
70     private static void closeSt(Statement st) {
71         try {
72             if(st != null) {
73                 st.close();
74             }
75         }catch(SQLException e) {
76             e.printStackTrace();
77         }finally {
78             st = null;
79         }
80     }
81     
82     private static void closeConn(Connection conn) {
83         try {
84             if(conn != null) {
85                 conn.close();
86             }
87         }catch(SQLException e) {
88             e.printStackTrace();
89         }finally {
90             conn = null;
91         }
92     }
93 }

url=jdbc:mysql://localhost/mydb?user=root&password=root
driverClass=com.mysql.jdbc.Driver