JDBC基础操作汇总

基础的工具类

JDBC进行CRUD操作会有很多重复的代码，我们把重复的代码汇总到一个类里就可以让程序变得简洁很多

package JDBCLearning;import javax.xml.transform.Result;
import java.sql.*;
import java.util.ArrayList;/*** Created by junk beat on 2019/2/22.*/
public class jdbcUtil {//连接数据库的基础信息private static final String connectionURL = "jdbc:mysql://localhost:3306/web01?useUnicode=true&characterEncoding=UTF-8";private static final String username = "root";  //登录数据库的账号private static final String password = "root";  //登录数据库的密码//建立连接public static Connection createConnection(){try{Class.forName("com.mysql.jdbc.Driver");return DriverManager.getConnection(connectionURL, username, password);} catch (ClassNotFoundException e){e.printStackTrace();} catch (SQLException e){e.printStackTrace();}return null;    //建立连接失败返回空指针}//关闭连接操作public static void close(ResultSet rs, Statement stmt, Connection con){closeResult(rs);closeStatement(stmt);closeConnection(con);}//关闭结果集private static void closeResult(ResultSet rs){try {if (rs != null) rs.close();} catch (SQLException e){e.printStackTrace();}}//关闭语句执行声明private static void closeStatement(Statement stmt){try {if (stmt != null) stmt.close();} catch (SQLException e){e.printStackTrace();}}//关闭连接private static void closeConnection(Connection con){try {if (con != null) con.close();} catch (SQLException e){e.printStackTrace();}}
}

表的结构

我们创建一个简单的表进行测试

use web01;
/*创建表*/
drop table if exists test;
create table test (id int primary key auto_increment,username varchar(16) not null unique,password varchar(16) not null,account int default 5000
);/*插入数据*/
insert into test (username, password) values ("王大柱", "123456");
insert into test (username, password) values ("Ben", "123456");
insert into test (username, password) values ("White", "123456");
insert into test (username, password) values ("Jessis Pinkman", "123456");
insert into test (username, password) values ("Hank", "123456");
insert into test (username, password) values ("王兰花", "123456");
insert into test (username, password) values ("李铁蛋", "123456");

selectAll方法

查询表中所有数据的方法

    //查询所有结果方法public static void selectAll(String tableName){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();stmt = con.createStatement();rs = stmt.executeQuery("select * from " + tableName);//执行sql语句while(rs.next()){System.out.println(rs.getInt(1)+","+rs.getString(2)+","+rs.getString(3)+","+rs.getInt(4));}} catch (SQLException e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}

登录效验

   //登录效验public static boolean selectByUsernamePassword(String username, String password){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();stmt = con.createStatement();String sql = "select * from test where username = '"+username+"' and password = '"+password+"'";rs = stmt.executeQuery(sql);if(rs.next()){System.out.println("登录成功");return true;} else {System.out.println("登录失败");return false;}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}System.out.println("登录失败");return false;}

防止SQL注入的登录效验

    //防止SQL注入的登录效验public static boolean selectByUP(String username, String password){Connection con = null;PreparedStatement pstmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "select * from test where username = ? and password = ?";pstmt = con.prepareStatement(sql);pstmt.setString(1, username);pstmt.setString(2, password);rs = pstmt.executeQuery();if(rs.next()){System.out.println("登录成功");return true;} else {System.out.println("登录失败");return false;}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, pstmt, con);}System.out.println("登录失败");return false;}

分页查询

查询的数据是从 (page - 1)*count 到 count

    //分页查询//参数分别是要查询的页数和每一页有多少行数据public static void PagingQuery(int page, int count){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "select * from test limit " + (page - 1) * count + ", " + count;stmt = con.createStatement();rs = stmt.executeQuery(sql);while(rs.next()){System.out.println(rs.getInt(1)+","+rs.getString(2)+","+rs.getString(3)+","+rs.getInt(4));}} catch (SQLException e){e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}

插入，删除和修改操作

    //插入，删除和修改操作public static void insert(String username, String password){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "insert into test (username, password) values (?, ?)";stmt = con.prepareStatement(sql);stmt.setString(1, username);stmt.setString(2, password);int result = stmt.executeUpdate();  //返回值代表受到影响的行数if(result != -1){System.out.println("插入成功");}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}public static void delete(String username){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = JDBCUtils.getConnection();String sql = "delete from test where username = ?";stmt = con.prepareStatement(sql);stmt.setString(1, username);int result = stmt.executeUpdate();if(result > 0){System.out.println("删除成功");}} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.closeP(rs, stmt, con);}}public static void update(String username, String newPassword){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "update test set password = ? where username = ?";stmt = con.prepareStatement(sql);stmt.setString(1,newPassword);stmt.setString(2, username);int result = stmt.executeUpdate();if(result > 0){System.out.println("修改成功");}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}

事务操作

    //事务操作public static void transferAccounts(String username1, String username2, int money){Connection con = null;PreparedStatement stmt1 = null;PreparedStatement stmt2 = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();//开启事务con.setAutoCommit(false);  //是否自动提交String sql = "update test set account = account - ? where username = ?";stmt1 = con.prepareStatement(sql);stmt1.setInt(1,money);stmt1.setString(2, username1);stmt1.executeUpdate();//String s = null;//s.charAt(2);sql = "update test set account = account + ? where username = ?";stmt2 = con.prepareStatement(sql);stmt2.setInt(1,money);stmt2.setString(2, username2);stmt2.executeUpdate();con.commit();   //提交事务} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt1, stmt2, con);}}

连接池

使用完后归还到ArrayList，不用关闭，这样就可以节省创建连接的时间

    private static ArrayList<Connection> conList = new ArrayList<Connection>();//静态代码块先于方法执行static {for(int i=0; i<5; i++){Connection con = createConnection();conList.add(con);}}public static Connection getConnection(){if(conList.isEmpty()==false){Connection con = conList.get(0);conList.remove(con);    //移除return con;} else {return createConnection(); //创建一个新链接}}

所有代码汇总

package JDBCLearning;import java.sql.*;/*** Created by junk beat on 2019/2/22.*/
public class JDBCop {public static void main(String[] args) throws SQLException{//selectAll("test");//selectByUsernamePassword("王兰花","123456");//selectByUP("王兰花","123456");//PagingQuery(1, 5);//insert("李大嘴", "1235480");//delete("李大嘴");//update("王兰花","5462145");transferAccounts("王兰花","White", 1000);}//查询所有结果方法public static void selectAll(String tableName){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();stmt = con.createStatement();rs = stmt.executeQuery("select * from " + tableName);//执行sql语句while(rs.next()){System.out.println(rs.getInt(1)+","+rs.getString(2)+","+rs.getString(3)+","+rs.getInt(4));}} catch (SQLException e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}//登录效验public static boolean selectByUsernamePassword(String username, String password){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();stmt = con.createStatement();String sql = "select * from test where username = '"+username+"' and password = '"+password+"'";rs = stmt.executeQuery(sql);if(rs.next()){System.out.println("登录成功");return true;} else {System.out.println("登录失败");return false;}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}System.out.println("登录失败");return false;}//防止SQL注入的登录效验public static boolean selectByUP(String username, String password){Connection con = null;PreparedStatement pstmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "select * from test where username = ? and password = ?";pstmt = con.prepareStatement(sql);pstmt.setString(1, username);pstmt.setString(2, password);rs = pstmt.executeQuery();if(rs.next()){System.out.println("登录成功");return true;} else {System.out.println("登录失败");return false;}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, pstmt, con);}System.out.println("登录失败");return false;}//分页查询//参数分别是要查询的页数和每一页有多少行数据public static void PagingQuery(int page, int count){Connection con = null;Statement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "select * from test limit " + (page - 1) * count + ", " + count;stmt = con.createStatement();rs = stmt.executeQuery(sql);while(rs.next()){System.out.println(rs.getInt(1)+","+rs.getString(2)+","+rs.getString(3)+","+rs.getInt(4));}} catch (SQLException e){e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}//插入，删除和修改操作public static void insert(String username, String password){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "insert into test (username, password) values (?, ?)";stmt = con.prepareStatement(sql);stmt.setString(1, username);stmt.setString(2, password);int result = stmt.executeUpdate();  //返回值代表受到影响的行数if(result != -1){System.out.println("插入成功");}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}public static void delete(String username){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = JDBCUtils.getConnection();String sql = "delete from test where username = ?";stmt = con.prepareStatement(sql);stmt.setString(1, username);int result = stmt.executeUpdate();if(result > 0){System.out.println("删除成功");}} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.closeP(rs, stmt, con);}}public static void update(String username, String newPassword){Connection con = null;PreparedStatement stmt = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();String sql = "update test set password = ? where username = ?";stmt = con.prepareStatement(sql);stmt.setString(1,newPassword);stmt.setString(2, username);int result = stmt.executeUpdate();if(result > 0){System.out.println("修改成功");}} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt, con);}}//事务操作public static void transferAccounts(String username1, String username2, int money){Connection con = null;PreparedStatement stmt1 = null;PreparedStatement stmt2 = null;ResultSet rs = null;try {con = jdbcUtil.createConnection();//开启事务con.setAutoCommit(false);  //是否自动提交String sql = "update test set account = account - ? where username = ?";stmt1 = con.prepareStatement(sql);stmt1.setInt(1,money);stmt1.setString(2, username1);stmt1.executeUpdate();//String s = null;//s.charAt(2);sql = "update test set account = account + ? where username = ?";stmt2 = con.prepareStatement(sql);stmt2.setInt(1,money);stmt2.setString(2, username2);stmt2.executeUpdate();con.commit();   //提交事务} catch (Exception e) {e.printStackTrace();} finally {jdbcUtil.close(rs, stmt1, stmt2, con);}}
}

工具类

package JDBCLearning;import javax.xml.transform.Result;
import java.sql.*;
import java.util.ArrayList;/*** Created by junk beat on 2019/2/22.*/
public class jdbcUtil {//连接数据库的基础信息private static final String connectionURL = "jdbc:mysql://localhost:3306/web01?useUnicode=true&characterEncoding=UTF-8";private static final String username = "root";  //登录数据库的账号private static final String password = "root";  //登录数据库的密码private static ArrayList<Connection> conList = new ArrayList<Connection>();//静态代码块先于方法执行static {for(int i=0; i<5; i++){Connection con = createConnection();conList.add(con);}}public static Connection getConnection(){if(conList.isEmpty()==false){Connection con = conList.get(0);conList.remove(con);    //移除return con;} else {return createConnection(); //创建一个新链接}}//建立连接public static Connection createConnection(){try{Class.forName("com.mysql.jdbc.Driver");return DriverManager.getConnection(connectionURL, username, password);} catch (ClassNotFoundException e){e.printStackTrace();} catch (SQLException e){e.printStackTrace();}return null;    //建立连接失败返回空指针}//关闭连接操作public static void close(ResultSet rs, Statement stmt, Connection con){closeResult(rs);closeStatement(stmt);closeConnection(con);}public static void close(ResultSet rs, PreparedStatement pstmt, Connection con){closeResult(rs);closePrepareStatement(pstmt);closeConnection(con);}public static void close(ResultSet rs, PreparedStatement pstmt1, PreparedStatement pstmt2, Connection con){closeResult(rs);closePrepareStatement(pstmt1);closePrepareStatement(pstmt2);closeConnection(con);}//关闭结果集private static void closeResult(ResultSet rs){try {if (rs != null) rs.close();} catch (SQLException e){e.printStackTrace();}}//关闭语句执行声明private static void closeStatement(Statement stmt){try {if (stmt != null) stmt.close();} catch (SQLException e){e.printStackTrace();}}//关闭pstmtprivate static void closePrepareStatement(PreparedStatement pstmt){try {if (pstmt != null) pstmt.close();} catch (SQLException e){e.printStackTrace();}}//关闭连接private static void closeConnection(Connection con){try {if (con != null) con.close();} catch (SQLException e){e.printStackTrace();}}
}

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JDBC基础操作汇总

基础的工具类

表的结构

selectAll方法

登录效验

防止SQL注入的登录效验

分页查询

插入，删除和修改操作

事务操作

所有代码汇总

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