java实现的数据库管理类(mysql)_MySQL

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

public class DBManager {

 /**
 * 该方法用户连接数据库
 * 
 * @return 返回Connection的一个实例
 */
 private Connection getConnection() {

 Connection con = null;

 try {
 Class.forName(StaticVar.DRIVER_NAME).newInstance();

 con = DriverManager.getConnection(StaticVar.DB_URL,
 StaticVar.USER_NAME, StaticVar.DB_PASSWD);

 } catch (InstantiationException e) {
 return null;
 } catch (IllegalAccessException e) {
 return null;
 } catch (ClassNotFoundException e) {
 return null;
 } catch (SQLException e) {
 return null;
 }

 return con;
 }

 /**
 * 用于查询sql语句
 * 
 * @param sql
 * sql语句
 * @return 返回ResultSet集合
 */
 public ResultSet select(String sql) {
 ResultSet res = null;

 Connection con = getConnection();

 Statement state = null;

 if (!(con == null)) {

 try {
 state = con.createStatement();
 res = state.executeQuery(sql);
 } catch (SQLException e) {
 return null;
 }

 }

 if (state != null) {
 try {
 state.close();
 } catch (SQLException e) {
 return null;
 }
 }

 if (con != null) {
 try {
 con.close();
 } catch (SQLException e) {
 return null;
 }
 }

 return res;
 }

 /**
 * 向表中插入一个元素，返回插入后的元素的id
 * 
 * @param sql
 * @return
 */
 public int insert(String sql) {
 int iId = -1;

 Connection con = getConnection();

 Statement state = null;

 if (con != null) {
 try {
 state = con.createStatement();

 int res = state.executeUpdate(sql,
 Statement.RETURN_GENERATED_KEYS);

 if (res != 0) {
 ResultSet rs = state.getGeneratedKeys();
 if (rs.next()) {
 iId = rs.getInt(1);
 }
 }
 } catch (SQLException e) {
 iId = -1;
 }

 }

 if (state != null) {
 try {
 state.close();
 } catch (SQLException e) {
 }
 }

 if (con != null) {
 try {
 con.close();
 } catch (SQLException e) {
 }
 }

 return iId;
 }

 /**
 * 修改表中的某个元素的数值
 * 
 * @param sql
 * sql语句
 * @return 元素是否被成功修改
 */
 public boolean update(String sql) {
 boolean updated = false;

 Connection con = getConnection();
 Statement state = null;

 if (con != null) {
 try {
 state = con.createStatement();

 int res = state.executeUpdate(sql);

 if (res == 0) {
 updated = false;
 } else {
 updated = true;
 }
 } catch (SQLException e) {
 updated = false;
 }

 }

 if (state != null) {
 try {
 state.close();
 } catch (SQLException e) {
 }
 }

 if (con != null) {
 try {
 con.close();
 } catch (SQLException e) {
 }
 }

 return updated;
 }

 /**
 * 删除表中的某一个表项
 * 
 * @param sql
 * sql语句
 * @return 返回是否删除成功
 */
 public boolean delete(String sql) {
 boolean deleted = false;

 Connection con = getConnection();

 Statement state = null;

 if (con != null) {
 try {
 state = con.createStatement();

 int res = state.executeUpdate(sql);

 if (res == 0) {
 deleted = false;
 } else {
 deleted = true;
 }

 } catch (SQLException e) {
 deleted = false;
 }

 }

 if (state != null) {
 try {
 state.close();
 } catch (SQLException e) {
 }
 }

 if (con != null) {
 try {
 con.close();
 } catch (SQLException e) {
 }
 }

 return deleted;
 }

}

public class StaticVar {

 public static final String DB_URL = "jdbc:mysql://localhost/db_test?useUnicode=true&characterEncoding=UTF-8";

 public static final String USER_NAME = "chen";
 public static final String DB_PASSWD = "******";
 public static final String DRIVER_NAME = "com.mysql.jdbc.Driver";



}