Java基礎開發之JDBC操作資料庫增刪改查,分頁查詢例項詳解
阿新 • • 發佈:2020-02-20
對資料庫的操作無非就是增刪改查,其中數查詢操作最為複雜,所以將查詢單獨講解,我這裡用的Mysql資料庫
增刪改查操作
分頁查詢操作
1.查詢結果以list返回
2.查詢結果以jsonArray返回
3.查詢總記錄條數
先看一下相關的配置資訊
public static final String USER_NAME = "root"; public static final String PWD = "123456789"; public static final String DRIVER = "com.mysql.jdbc.Driver"; public static final String URL = "jdbc:mysql://localhost:3306/web_demon"; /** 分頁查詢預設每頁記錄條數 */ public static final int PAGE_SIZE_DEFAULT = 10;
增刪改操作
獲取資料庫連線物件
/** * 獲取資料庫連線 * @return 資料庫連線物件 */ public Connection getConnection(Connection conn) { if(conn == null){ try { Class.forName(Config.DRIVER); conn = DriverManager.getConnection(Config.URL,Config.USER_NAME,Config.PWD); } catch (Exception e) { e.printStackTrace(); } } return conn; }
封裝增刪改操作
/** * 新增,刪除,插入操作 * @param sql 執行的sql語句 * 例如:新增語句 "insert into user (name,sex) values (?,?)"; * 刪除語句 "delete from user where id=?"; * 修改語句 "update user set name=?,sex=? where id=? and sex=?"; * @param values 對應的引數值 * @return 影響條數,-1為異常 */ private int execute(String sql,Object... values){ Connection conn = null; PreparedStatement pStmt = null; try { conn = this.getConnection(conn); pStmt = conn.prepareStatement(sql); //設定引數 if(pStmt != null && values != null && values.length > 0){ for (int i = 0; i < values.length; i++) { pStmt.setObject(i+1,values[i]); } } int i =pStmt.executeUpdate(); return i; } catch (Exception e) { e.printStackTrace(); } finally { if (conn != null) { this.closeConnection(conn); } } return -1; }
呼叫方法
//新增 public static void insert(){ String sql = "insert into user (name,?)"; Object[] values = new Object[]{"李四",0}; int res = baseImp.execute(sql,values); System.out.println("insert res="+res); } //刪除 public static void delete(){ String sql = "delete from user where id=?"; Object[] values = new Object[]{2}; int res = baseImp.execute(sql,values); System.out.println("delete res="+res); } //更新 public static void update(){ String sql = "update user set name=?,sex=? where id=? and sex=?"; Object[] values = new Object[]{"張三",1,values); System.out.println("update res="+res); }
查詢操作
1.查詢結果以list返回
/** * 查詢結果以list返回 * @param pageIndex 頁數 * @param pageSize 每頁記錄條數 * @param attachTableName 在結果集中是否給key值附加表名,例如:user.id,與id * @param sql 查詢語句 例如:"select u.id,u.name,u.sex,u.depart_id AS departId,d.* from user u,depart d where u.depart_id=d.id" * @param values * @throws SQLException */ private List<Map<String,Object>> queryList(int pageIndex,int pageSize,boolean attachTableName,String sql,Object... values) throws SQLException{ Connection conn = null; PreparedStatement pStmt = null; List<Map<String,Object>> dataList = null; //校驗引數 if(pageIndex <= 0){ pageIndex = 1; } if(pageSize <= 0){ pageSize = Config.PAGE_SIZE_DEFAULT; } conn = this.getConnection(conn); pStmt = conn.prepareStatement(sql); //設定引數 if(pStmt != null && values != null && values.length > 0){ for (int i = 0; i < values.length; i++) { pStmt.setObject(i+1,values[i]); } } //設定最大查詢到第幾條記錄 pStmt.setMaxRows(pageIndex*pageSize); ResultSet rs = pStmt.executeQuery(); //遊標移動到要輸出的第一條記錄 rs.relative((pageIndex-1)*pageSize); if(rs != null){ try { dataList = new ArrayList<Map<String,Object>>(); ResultSetMetaData md = rs.getMetaData(); //得到結果集(rs)的結構資訊,比如欄位數、欄位名等 //遍歷結果集 while(rs.next()){ Map<String,Object> map = new LinkedHashMap(); for (int i = 1; i <= md.getColumnCount(); i++) { map.put(attachTableName?(formatTableName(md.getTableName(i))+"."+md.getColumnLabel(i)):(md.getColumnLabel(i)),rs.getObject(i)); } dataList.add(map); } }finally{ if(rs != null){ rs.close(); } if(pStmt != null){ pStmt.close(); } if (conn != null) { this.closeConnection(conn); } } } return dataList; }
呼叫list查詢
public static void queryList(){ String sql = "select u.*,depart d where u.depart_id=d.id"; try { List<Map<String,Object>> dataList = baseImp.queryForListAttachTableName(2,2,sql,null); // List<Map<String,Object>> dataList = baseImp.queryForList(2,null); for (Map<String,Object> map : dataList) { for (String key : map.keySet()) { System.out.print(key+"="+map.get(key)+" "); } System.out.println(); } } catch (SQLException e) { e.printStackTrace(); } }
結果
2.查詢結果以jsonArray返回
/** * 查詢結果以ArrayList返回 * @param 在結果集中是否給key值附加表名,例如:user.id,depart d where u.depart_id=d.id" * @param values * @throws SQLException */ private JSONArray queryJsonArray(int pageIndex,Object... values) throws SQLException{ JSONArray jsonArray = null; Connection conn = null; PreparedStatement pStmt = null; //校驗引數 if(pageIndex <= 0){ pageIndex = 1; } if(pageSize <= 0){ pageSize = Config.PAGE_SIZE_DEFAULT; } conn = this.getConnection(conn); pStmt = conn.prepareStatement(sql); //設定引數 if(pStmt != null && values != null && values.length > 0){ for (int i = 0; i < values.length; i++) { pStmt.setObject(i+1,values[i]); } } //設定最大查詢到第幾條記錄 pStmt.setMaxRows(pageIndex*pageSize); ResultSet rs = pStmt.executeQuery(); //遊標移動到要輸出的第一條記錄 rs.relative((pageIndex-1)*pageSize); if(rs != null){ try { jsonArray = new JSONArray(); ResultSetMetaData md = rs.getMetaData(); //得到結果集(rs)的結構資訊,比如欄位數、欄位名等 //遍歷結果集 while(rs.next()){ JSONObject jsonObject = new JSONObject(); for (int i = 1; i <= md.getColumnCount(); i++) { jsonObject.put(attachTableName?(formatTableName(md.getTableName(i))+"."+md.getColumnLabel(i)):(md.getColumnLabel(i)),rs.getObject(i)+""); } jsonArray.add(jsonObject); } }finally{ if(rs != null){ rs.close(); } if(pStmt != null){ pStmt.close(); } if (conn != null) { this.closeConnection(conn); } } } return jsonArray; }
呼叫jsonArray查詢
public static void queryJsonArray(){ // String sql = "select * from user u"; String sql = "select u.*,depart d where u.depart_id=d.id"; // String sql = "select u.id AS uid,d.name from user u,depart d where u.depart_id=d.id"; // String sql = "select u.id,depart d where u.depart_id=d.id"; try { JSONArray jsonArray = baseImp.queryForJsonArrayAttachTableName(2,null); // JSONArray jsonArray = baseImp.queryForJsonArray(sql,null); System.out.println(jsonArray.toString()); for (int i = 0; i < jsonArray.size(); i++) { JSONObject jsonObject = jsonArray.getJSONObject(i); Iterator<?> iterator = jsonObject.keys(); Object key = null; while (iterator.hasNext()) { key = iterator.next(); System.out.print(key+" "+jsonObject.get(key)+" "); } System.out.println(); } } catch (SQLException e) { e.printStackTrace(); } }
結果
[{"user.id":"4","user.name":"王五","user.sex":"0","user.depart_id":"3","depart.id":"3","depart.name":"研發部","depart.desc":"這是研發部"},{"user.id":"5","user.name":"趙六","user.sex":"1","user.depart_id":"1","depart.id":"1","depart.name":"測試部","depart.desc":"這是測試部"}] user.id 4 user.name 王五 user.sex 0 user.depart_id 3 depart.id 3 depart.name 研發部 depart.desc 這是研發部 user.id 5 user.name 趙六 user.sex 1 user.depart_id 1 depart.id 1 depart.name 測試部 depart.desc 這是測試部
3.查詢總記錄條數
/** * 查詢記錄條數 * @param sql 例如:"select count(*) from user where xxx" * @param values * @throws SQLException */ public int queryCount(String sql,Object... values) throws SQLException{ int count = -1; Connection conn = null; PreparedStatement pStmt = null; conn = this.getConnection(conn); pStmt = conn.prepareStatement(sql); //設定引數 if(pStmt != null && values != null && values.length > 0){ for (int i = 0; i < values.length; i++) { pStmt.setObject(i+1,values[i]); } } ResultSet rs = pStmt.executeQuery(); if(rs != null){ try { while(rs.next()){ count = rs.getInt(1); } }finally{ if(rs != null){ rs.close(); } if(pStmt != null){ pStmt.close(); } if (conn != null) { this.closeConnection(conn); } } } return count; }
呼叫查詢總記錄條數
public static void queryCount(){ String sql = "select count(*) from user u"; try { System.out.println("count="+baseImp.queryCount(sql,null)); } catch (SQLException e) { e.printStackTrace(); } }
結果
至此我們介紹完了Java基礎開發中JDBC對資料庫進行增刪改查操作與分頁查詢,如果想了解更多關於這方面的文章大家可以檢視下面的相關連結