package com.jdbc.dbutils; import java.lang.reflect.Field; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import domain.UserInfo; public class JdbcUtils { //数据库用户名 private static final String USERNAME = "root"; //数据库密码 private static final String PASSWORD = "yanzi"; //驱动信息 private static final String DRIVER = "com.mysql.jdbc.Driver"; //数据库地址 private static final String URL = "jdbc:mysql://localhost:3306/mydb"; private Connection connection; private PreparedStatement pstmt; private ResultSet resultSet; public JdbcUtils() { // TODO Auto-generated constructor stub try{ Class.forName(DRIVER); System.out.println("数据库连接成功!"); }catch(Exception e){ } } /** * 获得数据库的连接 * @return */ public Connection getConnection(){ try { connection = DriverManager.getConnection(URL, USERNAME, PASSWORD); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return connection; } /** * 增加、删除、改 * @param sql * @param params * @return * @throws SQLException */ public boolean updateByPreparedStatement(String sql, List<Object>params)throws SQLException{ boolean flag = false; int result = -1; pstmt = connection.prepareStatement(sql); int index = 1; if(params != null && !params.isEmpty()){ for(int i=0; i<params.size(); i++){ pstmt.setObject(index++, params.get(i)); } } result = pstmt.executeUpdate(); flag = result > 0 ? true : false; return flag; } /** * 查询单条记录 * @param sql * @param params * @return * @throws SQLException */ public Map<String, Object> findSimpleResult(String sql, List<Object> params) throws SQLException{ Map<String, Object> map = new HashMap<String, Object>(); int index = 1; pstmt = connection.prepareStatement(sql); if(params != null && !params.isEmpty()){ for(int i=0; i<params.size(); i++){ pstmt.setObject(index++, params.get(i)); } } resultSet = pstmt.executeQuery();//返回查询结果 ResultSetMetaData metaData = resultSet.getMetaData(); int col_len = metaData.getColumnCount(); while(resultSet.next()){ for(int i=0; i<col_len; i++ ){ String cols_name = metaData.getColumnName(i+1); Object cols_value = resultSet.getObject(cols_name); if(cols_value == null){ cols_value = ""; } map.put(cols_name, cols_value); } } return map; } /**查询多条记录 * @param sql * @param params * @return * @throws SQLException */ public List<Map<String, Object>> findModeResult(String sql, List<Object> params) throws SQLException{ List<Map<String, Object>> list = new ArrayList<Map<String, Object>>(); int index = 1; pstmt = connection.prepareStatement(sql); if(params != null && !params.isEmpty()){ for(int i = 0; i<params.size(); i++){ pstmt.setObject(index++, params.get(i)); } } resultSet = pstmt.executeQuery(); ResultSetMetaData metaData = resultSet.getMetaData(); int cols_len = metaData.getColumnCount(); while(resultSet.next()){ Map<String, Object> map = new HashMap<String, Object>(); for(int i=0; i<cols_len; i++){ String cols_name = metaData.getColumnName(i+1); Object cols_value = resultSet.getObject(cols_name); if(cols_value == null){ cols_value = ""; } map.put(cols_name, cols_value); } list.add(map); } return list; } /**通过反射机制查询单条记录 * @param sql * @param params * @param cls * @return * @throws Exception */ public <T> T findSimpleRefResult(String sql, List<Object> params, Class<T> cls )throws Exception{ T resultObject = null; int index = 1; pstmt = connection.prepareStatement(sql); if(params != null && !params.isEmpty()){ for(int i = 0; i<params.size(); i++){ pstmt.setObject(index++, params.get(i)); } } resultSet = pstmt.executeQuery(); ResultSetMetaData metaData = resultSet.getMetaData(); int cols_len = metaData.getColumnCount(); while(resultSet.next()){ //通过反射机制创建一个实例 resultObject = cls.newInstance(); for(int i = 0; i<cols_len; i++){ String cols_name = metaData.getColumnName(i+1); Object cols_value = resultSet.getObject(cols_name); if(cols_value == null){ cols_value = ""; } Field field = cls.getDeclaredField(cols_name); field.setAccessible(true); //打开javabean的访问权限 field.set(resultObject, cols_value); } } return resultObject; } /**通过反射机制查询多条记录 * @param sql * @param params * @param cls * @return * @throws Exception */ public <T> List<T> findMoreRefResult(String sql, List<Object> params, Class<T> cls )throws Exception { List<T> list = new ArrayList<T>(); int index = 1; pstmt = connection.prepareStatement(sql); if(params != null && !params.isEmpty()){ for(int i = 0; i<params.size(); i++){ pstmt.setObject(index++, params.get(i)); } } resultSet = pstmt.executeQuery(); ResultSetMetaData metaData = resultSet.getMetaData(); int cols_len = metaData.getColumnCount(); while(resultSet.next()){ //通过反射机制创建一个实例 T resultObject = cls.newInstance(); for(int i = 0; i<cols_len; i++){ String cols_name = metaData.getColumnName(i+1); Object cols_value = resultSet.getObject(cols_name); if(cols_value == null){ cols_value = ""; } Field field = cls.getDeclaredField(cols_name); field.setAccessible(true); //打开javabean的访问权限 field.set(resultObject, cols_value); } list.add(resultObject); } return list; } /** * 释放数据库连接 */ public void releaseConn(){ if(resultSet != null){ try{ resultSet.close(); }catch(SQLException e){ e.printStackTrace(); } } } /** * @param args */ public static void main(String[] args) throws SQLException { // TODO Auto-generated method stub JdbcUtils jdbcUtils = new JdbcUtils(); jdbcUtils.getConnection(); /*******************增*********************/ /* String sql = "insert into userinfo (username, pswd) values (?, ?), (?, ?), (?, ?)"; List<Object> params = new ArrayList<Object>(); params.add("小明"); params.add("123xiaoming"); params.add("张三"); params.add("zhangsan"); params.add("李四"); params.add("lisi000"); try { boolean flag = jdbcUtils.updateByPreparedStatement(sql, params); System.out.println(flag); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }*/ /*******************删*********************/ //删除名字为张三的记录 /* String sql = "delete from userinfo where username = ?"; List<Object> params = new ArrayList<Object>(); params.add("小明"); boolean flag = jdbcUtils.updateByPreparedStatement(sql, params);*/ /*******************改*********************/ //将名字为李四的密码改了 /* String sql = "update userinfo set pswd = ? where username = ? "; List<Object> params = new ArrayList<Object>(); params.add("lisi88888"); params.add("李四"); boolean flag = jdbcUtils.updateByPreparedStatement(sql, params); System.out.println(flag);*/ /*******************查*********************/ //不利用反射查询多个记录 /* String sql2 = "select * from userinfo "; List<Map<String, Object>> list = jdbcUtils.findModeResult(sql2, null); System.out.println(list);*/ //利用反射查询 单条记录 String sql = "select * from userinfo where username = ? "; List<Object> params = new ArrayList<Object>(); params.add("李四"); UserInfo userInfo; try { userInfo = jdbcUtils.findSimpleRefResult(sql, params, UserInfo.class); System.out.print(userInfo); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
时间: 2024-10-13 00:38:42