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jdbc_相關代碼
2022-06-29 18:13:00 【靈主罪人】
一、statement執行sql語句（）
(1)工具類
package Zer.demo.util;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.sql.*;
import java.util.Properties;
public class JdbcUtils {
public static String driver;
public static String url;
public static String root;
public static String password;
static {
try {
//進行讀取資源,配置文件的
InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
//實例化配置文件對象拿取資源
Properties properties = new Properties();
//去加載讀取出來的資源
properties.load(in);
//將資源讀取出來儲存
driver = properties.getProperty("driver");
url = properties.getProperty("url");
root = properties.getProperty("root");
password = properties.getProperty("password");
//1.加載驅動
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
//2.獲取連接
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, root, password);
}
//3.釋放資源
public static void rslease(Connection coon, Statement st, ResultSet resultSet){
if (resultSet!=null){
try {
resultSet.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (st!=null){
try {
st.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (coon!=null){
try {
coon.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
}
}
(2)配置文件
名稱：db.Properties,自己在new中新建一個，圖標如下面
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=Asia/Shanghai
root=root
password=123456
1.删除
package Zer.demo.Caozuo;
import Zer.demo.util.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Delete {
public static void main(String[] args) {
Connection coon = null;
Statement st = null;
ResultSet resultSet = null;
try {
//調用了此方法，此時靜態代碼塊會自動執行。加載驅動已經執行了
coon = JdbcUtils.getConnection();
st = coon.createStatement();
String sql ="delete from grade where gradeid=25";
int i = st.executeUpdate(sql);
if (i>0){
System.out.println("删除成功");
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.rslease(coon,st,resultSet);
}
}
}
2.更新
package Zer.demo.Caozuo;
import Zer.demo.util.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Update {
public static void main(String[] args) {
Connection coon = null;
Statement st = null;
ResultSet resultSet = null;
try {
//調用了此方法，此時靜態代碼塊會自動執行。加載驅動已經執行了
coon = JdbcUtils.getConnection();
st = coon.createStatement();
String sql ="update grade set gradename='大家都一樣，即使不一樣，累一點也無妨' where gradeid= 22";
int i = st.executeUpdate(sql);
if (i>0){
System.out.println("更新成功");
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.rslease(coon,st,resultSet);
}
}
}
3.插入
package Zer.demo.Caozuo;
import Zer.demo.util.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Insert {
public static void main(String[] args) {
Connection coon = null;
Statement st = null;
ResultSet resultSet = null;
try {
//調用了此方法，此時靜態代碼塊會自動執行。加載驅動已經執行了
coon = JdbcUtils.getConnection();
st = coon.createStatement();
String sql ="insert into grade values(25,'沒有多餘失落可以走')";
int i = st.executeUpdate(sql);
if (i>0){
System.out.println("插入成功");
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.rslease(coon,st,resultSet);
}
}
}
4.查詢
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Select {
public static void main(String[] args) {
Connection coon = null;
Statement st = null;
ResultSet resultSet = null;
try {
//調用了此方法，此時靜態代碼塊會自動執行。加載驅動已經執行了
coon = JdbcUtils.getConnection();
st = coon.createStatement();
String sql= "SELECT * FROM grade";
//5、用創建的statement對象執行sql語句，返回結果集
resultSet = st.executeQuery(sql);
while (resultSet.next()){
System.out.println("gradeid="+resultSet.getObject("gradeid"));
System.out.println("gradename="+resultSet.getObject("gradename"));
System.out.println("………………………………………………………………………………………………………………………………………");
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.rslease(coon,st,resultSet);
}
}
}
如果用statement雖然容易理解上手，但是有SQL注入問題，容易出現安全隱患，為此推薦用preparestatement
5、SQL注入問題
stament存在SQL注入問題
package Zer.demo.util;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class Zhuru {
public static void main(String[] args) {
Login(14," 'or '1=1");
}
//業務語句
public static void Login(int password11,String yonghuming){
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection();
st= conn.createStatement();
String sql = "select * from grade where gradeid ='"+password11+"' and gradename='"+yonghuming+"'";
rs = st.executeQuery(sql);
while (rs.next()){
System.out.println(rs.getString("gradename"));
System.out.println(rs.getInt("gradeid"));
}
} catch (Exception throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.rslease(conn,st,rs);
}
}
}
二、Preparedstatement執行sql語句
(1)工具類
package Zer.demo.util;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
public class JdbcUtils1 {
public static String driver = null;
public static String url = null;
public static String root = null;
public static String password = null;
static {
try {
InputStream in = JdbcUtils1.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(in);
driver = properties.getProperty("driver");
url = properties.getProperty("url");
root = properties.getProperty("root");
password = properties.getProperty("password");
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getconnection() throws SQLException {
return DriverManager.getConnection(url,root,password);
}
public static void release(Connection conn, PreparedStatement pr, ResultSet rs){
if (rs!=null){
try {
rs.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (pr!=null){
try {
pr.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (conn!=null){
try {
conn.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
}
}
(2)配置文件
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=Asia/Shanghai
root=root
password=123456
1、删除
package Zer.demo.PrepareStatement;
import Zer.demo.util.JdbcUtils1;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class Delete1 {
public static void main(String[] args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JdbcUtils1.getconnection();
String sql = "delete from grade where gradeid = ?";//先寫SQL語句，‘？’是占比特符號
ps = conn.prepareStatement(sql);//進行預編譯，不執行
//手動執行SQL語句
ps.setInt(1, 26);
int i = ps.executeUpdate();
if (i > 0) {
System.out.println("删除成功");
} else {
System.out.println("删除失敗");
}
} catch (Exception throwables) {
throwables.printStackTrace();
} finally {
JdbcUtils1.release(conn, ps, rs);
}
}
}
## 2、更新
package Zer.demo.PrepareStatement;
import Zer.demo.util.JdbcUtils1;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class Update1 {
public static void main(String[] args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JdbcUtils1.getconnection();
String sql = "update grade set gradename = ? where gradeid = ?";//先寫SQL語句，‘？’是占比特符號
ps = conn.prepareStatement(sql);//進行預編譯，不執行
//手動執行SQL語句
ps.setString(1, "女子之道，學會自我愛護");
ps.setInt(2, 26);
int i = ps.executeUpdate();
if (i > 0) {
System.out.println("更新成功");
} else {
System.out.println("更新失敗");
}
} catch (Exception throwables) {
throwables.printStackTrace();
} finally {
JdbcUtils1.release(conn, ps, rs);
}
}
}
3、插入
package Zer.demo.PrepareStatement;
import Zer.demo.util.JdbcUtils1;
import java.sql.*;
public class Insert1 {
public static void main(String[] args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JdbcUtils1.getconnection();
String sql = "insert into grade(gradeid,gradename) values(?,?)";//先寫SQL語句，‘？’是占比特符號
ps = conn.prepareStatement(sql);//進行預編譯，不執行
//手動執行SQL語句
ps.setInt(1, 26);//第一個占比特符，賦值26
ps.setString(2, "君子之道，自我修養");//第二個占比特符，賦值君子之道，自我修養
int i = ps.executeUpdate();
if (i > 0) {
System.out.println("插入成功");
} else {
System.out.println("插入失敗");
}
} catch (Exception throwables) {
throwables.printStackTrace();
} finally {
JdbcUtils1.release(conn, ps, rs);
}
}
}
4、查詢
package Zer.demo.PrepareStatement;
import Zer.demo.util.JdbcUtils1;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class Select1 {
public static void main(String[] args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JdbcUtils1.getconnection();
String sql = "select * from grade";
String sql1 = "select * from grade";
ps = conn.prepareStatement(sql);//進行預編譯，不執行
//手動執行SQL語句,沒有占比特符就可以不用寫
rs = ps.executeQuery();
while (rs.next()) {
System.out.println(rs.getInt("gradeid"));
System.out.println(rs.getString("gradename"));
}
} catch (Exception throwables) {
throwables.printStackTrace();
} finally {
JdbcUtils1.release(conn, ps, rs);
}
}
}
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