学步园

转自：http://blog.csdn.net/ljjlzx/archive/2009/07/29/4390628.aspx

hibernate 可以使我们轻松的进行数据库的操作，
传递一个查询语句(类似 "select id,name from userInfo"),hibernate 会自动的将符合条件的
对象封装的list里面，供我们调用，大大简化了我们的代码量。下面就以一段代码模仿hibernate
的实现。

代码片段一(一般的查询方法)：
/**<br /> * 通用的查询方法<br /> * 通过SQL语句,与传递进来的object<br /> * 将查询出来的sql结果,通过反射机制封装至object<br /> * 注: ojbect必须为POJO,或BEAN的类<br /> * @param sql 查询SQL<br /> * @param objName 需要返回的列表内包含对象的类型<br /> * @return 封装好的对象<br /> */<br /> public List getResult(String sql,String objName,int db_flag) throws Exception<br /> {</p> <p> PreparedStatement stmt = null;<br /> ResultSet rs = null;<br /> RecordReflection rr = null;</p> <p> //获得数据库的连接<br /> dbConnection = new DbConn1().getDBConnection();<br /> if(dbConnection != null) System.out.println("GetConn successful");</p> <p> List result = null;<br /> try {<br /> stmt = dbConnection.prepareStatement(sql);<br /> rs = stmt.executeQuery();<br /> if(rs != null){<br /> System.out.println("GetRS successful");<br /> }<br /> //具体内容见代码片段2<br /> rr = new RecordReflection();<br /> //通过传递 结果集 和 “对象的全名” 返回 对象列表,和 普通查询 这一步不同<br /> result = rr.Relection(rs, objName);</p> <p> } catch (SQLException ex) {<br /> log.error("getResult is error:" + ex.getMessage());<br /> ex.printStackTrace();<br /> } finally {<br /> this.closeResultSet(rs);<br /> this.closeStatement(stmt);<br /> this.closeConnection();<br /> }</p> <p> return result; //返回范类型集合,该集合中存储着符合条件的行与列<br /> } 

代码片段二(RecordReflection 类)：
package com.ghrt.frame;<br /> import java.lang.reflect.Field;<br /> import java.lang.reflect.Method;<br /> import java.math.BigDecimal;<br /> import java.sql.ResultSet;<br /> import java.sql.ResultSetMetaData;<br /> import java.sql.Timestamp;<br /> import java.util.ArrayList;<br /> import java.util.Date;<br /> import java.util.Iterator;<br /> import java.util.List;<br /> import org.apache.log4j.Logger;<br /> public class RecordReflection {<br /> private Logger log = Logger.getLogger(RecordReflection.class);<br /> /**<br /> * 通过传递进来的ResultSet与对象名称,序列化为对象,塞入list<br /> * @param rs 结果集<br /> * @param objName 对象<br /> * @return list list里存储传递的objName的对象<br /> */<br /> public List Relection(ResultSet rs,String objName){<br /> List list = null;<br /> try{<br /> List resultList = this.ProcessResultSet(rs);<br /> list = this.ProcessObject(resultList, objName);</p> <p> }catch(Exception e){<br /> log.error("Relection is error:" + e.getMessage());<br /> }<br /> return list;<br /> }<br /> public List ProcessResultSet(ResultSet rs) throws PlatformException{</p> <p> List listResult =new ArrayList();<br /> int cols = 0;<br /> String colName="";<br /> String colType="";<br /> String colValue="";<br /> try{<br /> if(rs == null) //判断是否结果集为空,如果为空,直接返回<br /> return null;</p> <p> LabelValue lv = null; //见代码片段3</p> <p> List list = new ArrayList<LabelValue>();<br /> ResultSetMetaData rsetMd = null;<br /> rsetMd = rs.getMetaData();<br /> cols = rsetMd.getColumnCount();<br /> while(rs.next()){</p> <p> list = new ArrayList<LabelValue>();<br /> for (int i=0;i<cols;i++){<br /> colName = rsetMd.getColumnName(i+1);<br /> colType = rsetMd.getColumnTypeName(i+1);<br /> colValue = rs.getString(i+1);<br /> lv = new LabelValue();<br /> lv.setName(colName);<br /> lv.setType(colType);<br /> lv.setValue(colValue);</p> <p> list.add(lv);<br /> }</p> <p> listResult.add(list);<br /> }<br /> }catch(Exception e){<br /> log.error(" // Relection process ResultSet is error // " + e.getMessage());<br /> throw new PlatformException("class RecordReflection ProcessResultSet is error: " + e.getMessage());<br /> }<br /> return listResult;<br /> }<br /> public List ProcessObject(List list,String objName) throws PlatformException{</p> <p> List resultList = null;<br /> try{<br /> resultList = new ArrayList();<br /> log.debug(" // list.size:" + list.size());<br /> Iterator it = list.iterator();</p> <p> while(it.hasNext()){//获取每条记录<br /> List lvList = (List)it.next();<br /> log.debug(" // lvList.size:" + lvList.size());</p> <p> System.out.println("lvList:"+lvList.size());<br /> Iterator lvIt = lvList.iterator();</p> <p> Class clazz = Class.forName(objName);<br /> Object obj = clazz.newInstance();</p> <p> while(lvIt.hasNext()){//获取记录里的每个字段<br /> LabelValue lv = (LabelValue)lvIt.next();<br /> //获取生成的object对象</p> <p> Field[] fields = clazz.getDeclaredFields();<br /> log.debug("// fileds.length // "+fields.length);<br /> // for(Field field:fields){<br /> for(int i = 0;i<fields.length;i++){<br /> Field field = fields[i];<br /> System.out.println(fields[i]);<br /> log.debug("getname:"+field.getName()+" // lv.getName // "+lv.getName());<br /> String fieldName = field.getName();</p> <p> if(fieldName.equalsIgnoreCase(lv.getName())){<br /> log.debug(" // fieldName//" + fieldName +" // fieldType //" + field.getType().getName());<br /> log.debug(" // lv.getName // " + lv.getName() + " // lv.value // " + lv.getValue());<br /> Method method = clazz.getDeclaredMethod( "set"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1)<br /> ,new Class[]{field.getType()});<br /> if(field.getType().equals(String.class)){<br /> //处理当为String类型情况<br /> method.invoke(obj, new Object[]{this.toString(lv.getValue())});<br /> }else if(field.getType().equals(Integer.class)){<br /> //处理当为Integer类型情况<br /> method.invoke(obj, new Object[]{this.toInteger(lv.getValue())});<br /> }else if(field.getType().equals(Float.class)){<br /> //处理当为Float类型情况<br /> method.invoke(obj, new Object[]{this.toFloat(lv.getValue())});<br /> }else if(field.getType().equals(Double.class)){<br /> //处理当为Double类型情况<br /> method.invoke(obj, new Object[]{this.toDouble(lv.getValue())});<br /> }else if(field.getType().equals(BigDecimal.class)){<br /> //处理当为BigDecimal类型情况<br /> method.invoke(obj, new Object[]{this.toBigDecimal(lv.getValue())});<br /> }else if(field.getType().equals(Long.class)){<br /> //处理当为Long类型情况<br /> method.invoke(obj, new Object[]{this.toLong(lv.getValue())});<br /> }else if(field.getType().equals(Timestamp.class)){<br /> //处理当为Timestamp类型情况<br /> method.invoke(obj, new Object[]{this.toTimestamp(lv.getValue())});<br /> }else if(field.getType().equals(int.class)){<br /> //处理当为int类型情况<br /> method.invoke(obj, new Object[]{this.toInteger(lv.getValue())});<br /> }else if(field.getType().equals(float.class)){<br /> //处理当为float类型情况<br /> method.invoke(obj, new Object[]{this.toFloat(lv.getValue())});<br /> }else if(field.getType().equals(double.class)){<br /> //处理当为double类型情况<br /> method.invoke(obj, new Object[]{this.toDouble(lv.getValue())});<br /> }else if(field.getType().equals(Date.class)){<br /> //处理当为Date类型情况<br /> method.invoke(obj, new Object[]{this.toTimestamp(lv.getValue())});<br /> }else if(field.getType().equals(short.class)){<br /> //处理当为Short类型情况<br /> log.debug(" // parse short // ");<br /> method.invoke(obj, new Object[]{this.toShort(lv.getValue())});<br /> }</p> <p> }</p> <p> }<br /> }</p> <p> resultList.add(obj);<br /> }<br /> }catch(Exception ex){<br /> log.error(" // process object is error // " + ex.getMessage());<br /> throw new PlatformException("class RecordReflection ProcessObject is error: " + ex.getMessage());<br /> }<br /> return resultList;<br /> }<br /> /**<br /> * 对Date类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Date toDate(String args){<br /> Date result = null;<br /> if(null == args || "".equals(args))<br /> result = null;<br /> else<br /> try{<br /> // result = BigDecimal.parseBigDecimal(args);<br /> result = new Date(args);<br /> }catch(Exception e){<br /> result = null;<br /> log.error(" // RecordReflection parse Date is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对Timestamp类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Timestamp toTimestamp(String args){<br /> Timestamp result = null;<br /> if(null == args || "".equals(args))<br /> result = null;<br /> else<br /> try{<br /> // result = BigDecimal.parseBigDecimal(args);<br /> result = Timestamp.valueOf(args);<br /> }catch(Exception e){<br /> result = null;<br /> log.error(" // RecordReflection parse Timestamp is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对BigDecimal类型转换<br /> * @param args<br /> * @return<br /> */<br /> public BigDecimal toBigDecimal(String args){<br /> BigDecimal result = null;<br /> if(null == args || "".equals(args))<br /> result = new BigDecimal(0);<br /> else<br /> try{<br /> // result = BigDecimal.parseBigDecimal(args);<br /> result = new BigDecimal(args);<br /> }catch(Exception e){<br /> result = new BigDecimal(0);<br /> log.error(" // RecordReflection parse BigDecimal is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对Long类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Long toLong(String args){<br /> Long result = null;<br /> if(null == args || "".equals(args))<br /> result = new Long(0);<br /> else<br /> try{<br /> result = Long.parseLong(args);<br /> }catch(Exception e){<br /> result = new Long(0);<br /> log.error(" // RecordReflection parse Long is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对Double类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Double toDouble(String args){<br /> Double result = null;<br /> if(null == args || "".equals(args))<br /> result = new Double(0);<br /> else<br /> try{<br /> result = Double.parseDouble(args);<br /> }catch(Exception e){<br /> result = new Double(0);<br /> log.error(" // RecordReflection parse Double is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对Float类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Float toFloat(String args){<br /> Float result = null;<br /> if(null == args || "".equals(args))<br /> result = new Float(0);<br /> else<br /> try{<br /> result = Float.parseFloat(args);<br /> }catch(Exception e){<br /> result = new Float(0);<br /> log.error(" // RecordReflection parse Float is error // " + e.getMessage());<br /> }</p> <p> return result;<br /> }<br /> /**<br /> * 对Integer类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Integer toInteger(String args){<br /> Integer result = null;<br /> if(null == args || "".equals(args))<br /> result = 0;<br /> else{<br /> try{<br /> result = Integer.parseInt(args);<br /> }catch(Exception e){<br /> result = 0;<br /> log.error(" // RecordReflection parse Integer is error // " + e.getMessage());<br /> }<br /> }<br /> return result;<br /> }<br /> /**<br /> * 对Short类型转换<br /> * @param args<br /> * @return<br /> */<br /> public Short toShort(String args){<br /> Short result = null;<br /> if(null == args || "".equals(args))<br /> result = 0;<br /> else{<br /> try{<br /> result = Short.parseShort(args);<br /> }catch(Exception e){<br /> result = 0;<br /> log.error(" // RecordReflection parse Short is error // " + e.getMessage());<br /> }<br /> }<br /> return result;<br /> }<br /> /**<br /> * 重写了对String类型的转换<br /> * @param args<br /> * @return<br /> */<br /> public String toString(String args){<br /> String result = null;<br /> if (null == args || "".equals(args))<br /> result = "";<br /> else<br /> result = args.toString();<br /> return result;<br /> }<br /> } 

代码片段3(LabelValue 类):

package com.ghrt.frame;<br /> import java.io.Serializable;<br /> public class LabelValue implements Serializable{<br /> private String name;<br /> private String value;<br /> private String type;<br /> private int id;<br /> public String getName() {<br /> return name;<br /> }<br /> public void setName(String name) {<br /> this.name = name;<br /> }<br /> public String getValue() {<br /> return value;<br /> }<br /> public void setValue(String value) {<br /> this.value = value;<br /> }<br /> public String getType() {<br /> return type;<br /> }<br /> public void setType(String type) {<br /> this.type = type;<br /> }<br /> }<br />