jdbc通用查询通过map替代实体
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从10年做一个项目时，由于项目中需要做大量的查询功能，所以觉得如果使用传统的方式去做查询的话，就需要构建很多实体，比较繁琐，而且我们项目的特征是只需要做查询，不需要做新增，修改等操作，所以对此我写了一个公共类来处理此问题。
传统方式：传入sql，返回结果集，然后便利结果集封装实体List。
我的方式：传入sql，返回List。List中装的是map，而map中的key对应sql中的列，map中的value对应列的值。
备注：由于部分代码牵扯到公司的一些公共包，所以代码不能直接运行，请大家下载代码后做相应的改动，请谅解。如需我提供可直接运行的实例，请回复此贴联系我。
代码有问题的请批评指正。
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主要代码：
import java.math.BigDecimal;import java.sql.Clob;import java.sql.Date;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.sql.Time;import java.sql.Timestamp;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;/** * @描述：利用jdbc进行常见的查询 * @author richersky * @日期：2010-06-27 */public class EntityDaoImplJdbc {private String datasourse;/** * 根据sql语句查询数据 * @param sql * @param page * @return * @throws Exception */public Page findSql(String sql, Page page) throws Exception{JdbcUtil jdbcUtil = null;try {StringBuffer ssql = new StringBuffer();ssql.append(sql);//获取条件对应的值集合List valueList = page.getValues();LogUtil.infoSql(EntityDaoImplJdbc.class,valueList,"SQL语句:",ssql.toString());jdbcUtil = new JdbcUtil(datasourse);PreparedStatement preparedStatement = jdbcUtil.createPreparedStatement(ssql.toString());int liSQLParamIndex = 1;if(valueList!=null){for(int i=0;i<valueList.size();i++){Object obj = valueList.get(i);this.setParameterValue(preparedStatement, i+1, obj);liSQLParamIndex++;}}ResultSet rs = preparedStatement.executeQuery();List<Map<String,Object>> dataList = new ArrayList<Map<String,Object>>();Map<String,Integer> metaDataMap = null;while(rs.next()){if(rs.isFirst()){metaDataMap = this.getMetaData(rs);}dataList.add(this.setData(rs,metaDataMap));}page.setDataList(dataList);}catch (Exception e) {LogUtil.error(this.getClass(), e,"利用jdbc进行查询时出错！");throw e;}finally{if(jdbcUtil!=null){jdbcUtil.freeCon();}}return page;}/** * 根据sql查询出单条记录 * @param sql * @return Map<String,Object> * @throws Exception */public Map<String,Object> findUniqueBySql(String sql,List<Object> valueList) throws Exception{JdbcUtil jdbcUtil = null;Map<String,Object> map = null;try {LogUtil.infoSql(EntityDaoImplJdbc.class,valueList,"SQL语句:",sql);jdbcUtil = new JdbcUtil(datasourse);PreparedStatement preparedStatement= jdbcUtil.createPreparedStatement(sql);if(valueList!=null){for(int i=0;i<valueList.size();i++){Object obj = valueList.get(i);this.setParameterValue(preparedStatement, i+1, obj);}}ResultSet rs = preparedStatement.executeQuery();Map<String,Integer> metaDataMap = null;if(rs.next()){metaDataMap = this.getMetaData(rs);map = this.setData(rs,metaDataMap);}}catch (Exception e) {LogUtil.error(this.getClass(), e,"利用jdbc进行查询时出错！");throw e;}finally{if(jdbcUtil!=null){jdbcUtil.freeCon();}}return map;}/** * 设置PreparedStatement预处理sql语句的值 * @param pStatement * @param piIndex * @param pValueObject * @throws Exception */private void setParameterValue(PreparedStatement pStatement, int piIndex,Object pValueObject) throws Exception {if (pValueObject instanceof String) {pStatement.setString(piIndex, (String) pValueObject);} else if (pValueObject instanceof Boolean) {pStatement.setBoolean(piIndex, ((Boolean) pValueObject).booleanValue());} else if (pValueObject instanceof Byte) {pStatement.setByte(piIndex, ((Byte) pValueObject).byteValue());} else if (pValueObject instanceof Short) {pStatement.setShort(piIndex, ((Short) pValueObject).shortValue());} else if (pValueObject instanceof Integer) {pStatement.setInt(piIndex, ((Integer) pValueObject).intValue());} else if (pValueObject instanceof Long) {pStatement.setLong(piIndex, ((Long) pValueObject).longValue());} else if (pValueObject instanceof Float) {pStatement.setFloat(piIndex, ((Float) pValueObject).floatValue());} else if (pValueObject instanceof Double) {pStatement.setDouble(piIndex, ((Double) pValueObject).doubleValue());} else if (pValueObject instanceof BigDecimal) {pStatement.setBigDecimal(piIndex, (BigDecimal) pValueObject);} else if (pValueObject instanceof Date) {pStatement.setDate(piIndex, (Date) pValueObject);} else if (pValueObject instanceof Time) {pStatement.setTime(piIndex, (Time) pValueObject);} else if (pValueObject instanceof Timestamp) {pStatement.setTimestamp(piIndex, (Timestamp) pValueObject);} else {pStatement.setObject(piIndex, pValueObject);}}/** * 根据传入的结果集返回结果集的元数据，以列名为键以列类型为值的map对象 * @param rs * @return * @throws SQLException */private Map<String,Integer> getMetaData(ResultSet rs) throws SQLException{Map<String,Integer> map = new HashMap<String,Integer>();ResultSetMetaData metaData = rs.getMetaData(); int numberOfColumns = metaData.getColumnCount(); for(int column = 0; column < numberOfColumns; column++) { String columnName = metaData.getColumnLabel(column+1); int colunmType = metaData.getColumnType(column+1); columnName = columnName.toLowerCase(); map.put(columnName, colunmType); } return map;}/** * 将结果集封装为以列名存储的map对象 * @param rs * @param metaDataMap元数据集合 * @return * @throws Exception */private Map<String,Object> setData(ResultSet rs,Map<String,Integer> metaDataMap) throws Exception {Map<String,Object> map = new HashMap<String,Object>();for (String columnName : metaDataMap.keySet()) {int columnType = metaDataMap.get(columnName);Object object = rs.getObject(columnName);if(object==null){map.put(columnName, null);continue;}//以下并为对所有的数据类型做处理，未特殊处理的数据类型将以object的形式存储。switch (columnType) {case java.sql.Types.VARCHAR:map.put(columnName, object);break;case java.sql.Types.DATE:map.put(columnName, DateUtil.format(object.toString()));break;case java.sql.Types.TIMESTAMP:map.put(columnName, DateUtil.format(object.toString()));break;case java.sql.Types.TIME:map.put(columnName, DateUtil.format(object.toString()));break;case java.sql.Types.CLOB:try{if(object!=null){Clob clob = (Clob)object;long length = clob.length();map.put(columnName, clob.getSubString(1L, (int)length));}}catch(Exception e){LogUtil.error(this.getClass(), e,"将字段值从clob转换为字符串时出错@!");}break;case java.sql.Types.BLOB:map.put(columnName, "");break;default:map.put(columnName, object);break;}} return map;}}?