StrutsCRUD

package com.strutscrud.model.dao.data; import java.sql.Connection; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List; import org.apache.log4j.Logger; public abstract class AbstractDAO { private Connection con = null; private Statement stmt = null; private ResultSet rs = null; private Logger log=Logger.getLogger(this.getClass()); //关闭数据库以及相关资源 private void closeAll(){ if (rs != null) { try { rs.close(); } catch (SQLException e) { log.error("关闭ResultSet失败", e); e.printStackTrace(); } } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { log.error("关闭Statement失败", e); e.printStackTrace(); } } if (con != null) { try { con.close(); } catch (SQLException e) { log.error("关闭Connection失败", e); e.printStackTrace(); } } } // 执行一个SQL语句，返回1成功0失败 protected int executeUpdate(String sql){ try { con=ConFactory.getFactory().getConnection(); stmt = con.createStatement(); return stmt.executeUpdate(sql); } catch (SQLException e) { log.error("访问数据库失败", e); e.printStackTrace(); } finally { this.closeAll(); } return 0; } //执行一组SQL语句，伴随事务控制 protected int executeUpdate(String[] sql){ try { con=ConFactory.getFactory().getConnection(); con.setAutoCommit(false); stmt = con.createStatement(); for(int i=0;i<sql.length;i++){ stmt.executeUpdate(sql[i]); } con.commit(); return 1; } catch (SQLException e) { log.error("访问数据库失败", e); try { con.rollback(); //回滚... } catch (SQLException e1) { log.error("回滚失败", e1); e1.printStackTrace(); } e.printStackTrace(); return 0; } finally { this.closeAll(); //调用closeAll() } } // 通过SQL语句查询返回一组实体对象 protected List<?> findForList(String sql){ //TODO: getNewList是什么意思？this代表谁？ List<Object> list=this.getNewList(); Object obj=null; DynamicEntity entity=null; String key; String value; try { con =ConFactory.getFactory().getConnection(); stmt = con.createStatement(); rs = stmt.executeQuery(sql); //TODO: public interface ResultSetMetaData所属包java.sql ResultSetMetaData rem= rs.getMetaData(); int ccount=rem.getColumnCount(); while(rs.next()) { entity=new DynamicEntity(); for(int i=1;i<ccount+1;i++){ key=rem.getColumnName(i); value=rs.getString(key); entity.setValue(key, value); } obj=this.fillEntity(entity); list.add(obj); } return list; } catch (SQLException e) { log.error("访问数据库失败", e); e.printStackTrace(); } finally { this.closeAll(); } return list; } //通过SQL语句查询返回一个实体对象 protected Object findForEntity(String sql){ Object obj=null; DynamicEntity entity=null; String key; String value; try { con =ConFactory.getFactory().getConnection(); stmt = con.createStatement(); rs = stmt.executeQuery(sql); ResultSetMetaData rem= rs.getMetaData(); int ccount=rem.getColumnCount(); if (rs.next()) { entity=new DynamicEntity(); for(int i=1;i<ccount+1;i++){ key=rem.getColumnName(i); value=rs.getString(key); entity.setValue(key, value); } obj=this.fillEntity(entity); } return obj; } catch (SQLException e) { log.error("访问数据库失败", e); e.printStackTrace(); } finally { this.closeAll(); } return obj; } // 通过SQL语句查询返回一个字符串 //TODO: findForString的代码 protected String findForString(String sql){ try { con =ConFactory.getFactory().getConnection(); stmt = con.createStatement(); rs = stmt.executeQuery(sql); if (rs.next()) { return rs.getString(1); } } catch (SQLException e) { log.error("访问数据库失败", e); e.printStackTrace(); } finally { this.closeAll(); } return null; } //通过SQL语句查询返回一个数字，如记录的行数 protected Long findForLong(String sql){ try { con =ConFactory.getFactory().getConnection(); stmt = con.createStatement(); rs = stmt.executeQuery(sql); if (rs.next()) { return rs.getLong(1); } } catch (SQLException e) { log.error("访问数据库失败", e); e.printStackTrace(); } finally { this.closeAll(); } return null; } //实现类可覆盖此方法更换集合，默认是ArrayList，比如可以改成LinkList或者TreeList protected List<Object> getNewList(){ return new ArrayList<Object>(); } //实现类必须实现此方法完成数据的传递工作 protected abstract Object fillEntity(final DynamicEntity entity); }