关于JDBC连接MYSQL的操作问题

1、ConnectionManager封装

package com.woyi.luyou;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class ConnectionManager {
private static final String driver_class = "com.mysql.jdbc.Driver";
private static final String url = "jdbc:mysql://localhost:3306/test1";
private static final String user = "username";
private static final String password = "password";

public static Connection getConnection() {
Connection conn = null;
try {
Class.forName(driver_class);
System.out.println("Success loading Mysql Driver!");
conn = DriverManager.getConnection(url, user, password);
System.out.println("Success connect Mysql server!");
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}

public static void UpdateConnection(Connection conn, String sql) {
try {
if (conn != null && !(conn.isClosed())) {
PreparedStatement Statement = conn.prepareStatement(sql);
Statement.executeUpdate();
System.out.println("插入数据成功 ！");
}
} catch (SQLException e) {
e.printStackTrace();
}
}

public static ResultSet selectConnection(Connection conn, String s) {
ResultSet rs = null;
try {
if (conn != null && !(conn.isClosed())) {
PreparedStatement Statement = conn.prepareStatement(s);
rs = Statement.executeQuery();
}
} catch (SQLException e) {
e.printStackTrace();
}
return rs;
}

public static int updateConnection(Connection conn, String st) {
int i = 0;
try {
if (conn != null && !(conn.isClosed())) {
PreparedStatement Statement = conn.prepareStatement(st);
i = Statement.executeUpdate();
System.out.println("修改成功 ！");
System.out.println("修改了: " + i + " 行 !");
}
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}

public static void closeConnection(Connection conn) {
try {
if (conn != null && !(conn.isClosed())) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}

public static void closeResultSet(ResultSet rs) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
}

public static void closeStatement(PreparedStatement pStatement) {
if (pStatement != null) {
try {
pStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
pStatement = null;
}
}
}

2、Main函数

package com.woyi.luyou;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;

public class TestSQL {
public static void main(String[] args) {
Connection conn = null;
PreparedStatement pstate = null;
ResultSet rs = null;
String str1 = "123";
String str2 = "321";
String sql = "INSERT INTO ab VALUES(" + str1 + "," + str2 + ")";
String s = "SELECT * FROM ab";
String st = "UPDATE ab SET A = 222 WHERE B = 321";
if ((conn = ConnectionManager.getConnection()) != null) {
ConnectionManager.UpdateConnection(conn, sql);
ConnectionManager.updateConnection(conn, st);
try {
pstate = conn.prepareStatement(s);
rs = pstate.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
System.out.println("Querying SELECT * FROM ab");
int columnsNumber = rsmd.getColumnCount();
while (rs.next()) {
for (int i = 1; i <= columnsNumber; i++) {
if (i > 1)
System.out.print(",  ");
String columnValue = rs.getString(i);
System.out.print(columnValue + " " + rsmd.getColumnName(i));
}
System.out.println("");
}
} catch (SQLException e) {
e.printStackTrace();
}
ConnectionManager.closeConnection(conn);
ConnectionManager.closeStatement(pstate);
ConnectionManager.closeResultSet(rs);
}
}
}