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java 使用策略模式操作JDBC數(shù)據(jù)庫(kù)
1:構(gòu)造一個(gè)操作數(shù)據(jù)庫(kù)的工具類,可以獲得連接和釋放連接
public class DBUtil { private static Connection conn = null; static { //靜態(tài)初始?jí)K try { Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "root", "064319"); //初始化獲取連接 } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } /** * 釋放連接 * @param rs * @param psmt * @param conn * @throws SQLException */ public static void closeAll(ResultSet rs, PreparedStatement psmt, Connection conn) throws SQLException { if(rs != null) { rs.close(); } if(psmt != null) { psmt.close(); } if(conn != null) { conn.close(); } } /** * 獲取連接 * @return */ public static Connection getConnection() { return conn; } /** * 根據(jù)表的名字來(lái)獲得表的列信息 * @param tableName */ public static void getTableColumnInfoByTableName(String tableName) { Connection conn = getConnection(); ResultSet rs = null; PreparedStatement psmt = null; String sql = "select * from " + tableName; try { psmt = conn.prepareStatement(sql); rs = psmt.executeQuery(); ResultSetMetaData resultSetMetaData = rs.getMetaData(); for(int i = 1; i<= resultSetMetaData.getColumnCount(); i++) { System.out.println(resultSetMetaData.getColumnName(i)); } } catch (SQLException e) { e.printStackTrace(); } finally { try { closeAll(rs, psmt, conn); } catch (SQLException e) { e.printStackTrace(); } } } /** * 根據(jù)表的名字來(lái)獲得表的信息 * @param tableName */ public static void getTableInfoByTableName(String tableName) { Connection conn = getConnection(); PreparedStatement psmt = null; ResultSet rs = null; String sql = "select * from " + tableName; try { psmt = conn.prepareStatement(sql); rs = psmt.executeQuery(); while(rs.next()) { ResultSetMetaData resultSetMetaData = rs.getMetaData(); for(int i = 1; i<= resultSetMetaData.getColumnCount(); i++) { if(i < resultSetMetaData.getColumnCount()) { System.out.print(rs.getObject(resultSetMetaData.getColumnName(i)) + ", "); } else { System.out.print(rs.getObject(resultSetMetaData.getColumnName(i))); } } System.out.println(); } } catch (SQLException e) { e.printStackTrace(); } finally { try { closeAll(rs, psmt, conn); } catch (SQLException e) { e.printStackTrace(); } } } }
2:構(gòu)造一個(gè)操作數(shù)據(jù)庫(kù)的BaseDao類
public class BaseDao { /** * 根據(jù)一些參數(shù)來(lái)保存相應(yīng)的對(duì)象 * @param sql 要執(zhí)行的sql語(yǔ)句 * @param params 為sql語(yǔ)句中相應(yīng)的參數(shù)賦值 * @return */ protected boolean saveOrUpdate(String sql, Object[] params) { Connection conn = null; PreparedStatement psmt = null; boolean flag = false; conn = DBUtil.getConnection(); if(conn != null) { try { psmt = conn.prepareStatement(sql); for(int i = 1; i <= params.length; i++) { psmt.setObject(i, params[i-1]); } if(psmt.executeUpdate() > 0) { flag = true; } } catch (SQLException e) { e.printStackTrace(); } finally { try { DBUtil.closeAll(null, psmt, conn); } catch (SQLException e) { e.printStackTrace(); } } } return flag; } /** * 根據(jù)一定的參數(shù)獲得某個(gè)具體的對(duì)象 * @param sql 要執(zhí)行的sql語(yǔ)句 * @param params 為sql語(yǔ)句中相應(yīng)的參數(shù)賦值 * @return */ public Object queryForObject(String sql, Object[] params, RowMapForObject rowMapForObject) { Connection conn = null; PreparedStatement psmt = null; conn = DBUtil.getConnection(); Object obj = null; ResultSet rs = null; if(conn != null) { try { psmt = conn.prepareStatement(sql); if(params != null && params.length > 0) { for(int i = 1; i <= params.length; i++) { psmt.setObject(i, params[i - 1]); } } rs = psmt.executeQuery(); obj = rowMapForObject.rowMapForObject(rs); } catch (SQLException e) { e.printStackTrace(); } finally { try { DBUtil.closeAll(null, psmt, conn); } catch (SQLException e) { e.printStackTrace(); } } } return obj; } /** * 根據(jù)相應(yīng)的參數(shù)獲得查詢的結(jié)果集 * @param sql * @param params * @return */ public List queryForList(String sql, Object[] params, RowMapForList rowMapForList) { Connection conn = null; PreparedStatement psmt = null; conn = DBUtil.getConnection(); List list = null; ResultSet rs = null; if(conn != null) { try { psmt = conn.prepareStatement(sql); if(params != null && params.length > 0) { for(int i = 1; i <= params.length; i++) { psmt.setObject(i, params[i - 1]); } } rs = psmt.executeQuery(sql); list = new ArrayList(); list = rowMapForList.rowMapForList(rs); } catch (SQLException e) { e.printStackTrace(); } finally { try { DBUtil.closeAll(null, psmt, conn); } catch (SQLException e) { e.printStackTrace(); } } } return list; } }
3:新建一個(gè)StudentDao類,該類繼承自BaseDao,實(shí)現(xiàn)對(duì)Student的管理
public class StudentDao extends BaseDao { /** * 保存一個(gè)Student的信息 */ public boolean saveStudent(Student student) { String sql = "insert into t_student(name, age) values(?, ?)"; Object[] params = new Object[]{student.getName(), student.getAge()}; return super.saveOrUpdate(sql, params); } /** * 根據(jù)id獲得一個(gè)Student的信息 * @param id * @return */ public Student getStudentById(long id) { String sql = "select * from t_student where id=?"; Object[] params = new Object[]{id}; return (Student)super.queryForObject(sql, params, new RowMapForObject() { public Object rowMapForObject(ResultSet rs) { Student student = null; try { if(rs != null && rs.next()) { student = new Student(); student.setAge(rs.getInt(Student.AGE)); student.setId(rs.getLong(Student.ID)); student.setName(rs.getString(Student.NAME)); } } catch (SQLException e) { e.printStackTrace(); } return student; } }); } /** * 獲得所有Student的信息 * @return */ public List getStudentAll() { String sql = "select * from t_student"; List list = super.queryForList(sql, null, new RowMapForList() { @Override public List rowMapForList(ResultSet rs) { List list = null; try { if(rs != null) { list = new ArrayList(); while(rs.next()) { Student student = new Student(); student.setId(rs.getLong("id")); student.setAge(rs.getInt("age")); student.setName(rs.getString("name")); list.add(student); } } } catch(SQLException e) { e.printStackTrace(); } return list; } }); return list; } }
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