在我开始进一步编写我的解决方案之前,我有一个稍微有点理论性的问题要弄清楚......
背景。我需要在 2 个(或可能更多)MS Access 文件之间进行比较。
每个文件都应包含在其他文件中找到的数据。
由于我在使用 JDBC 和连接到 Access 结果集时遇到的“限制”(它们只能向前滚动!),我创建了对结果集结构进行建模的“java 对象”(类)。
本质上,我有一个对象,它模拟结果集中的单个记录行(让我们称之为 rowSet) 一个 resSet 对象然后有一个 rowSet 的“数组”。
但是,为了“加快速度”,我捕获了键和索引列中的值,并为相关的 rowSet 对象创建了一个“key_Index”的 hashMap。
我比较然后执行以下操作。
获取第一个 resSet 对象(用作主对象),从中收集各个 Key_Index 哈希图(我们称其为“aKey”....
现在使用这个“aKey”对象搜索其他可用的 resSet 对象,看看是否有任何包含与“aKey”中的值匹配的 key_Index 值。
然而,我刚刚有一个相当烦人的想法。
如果我在我的其他 resSet 对象之一上使用代码 resSet.get(aKey) 我会遇到问题,因为“aKey”对象显然不是同一个对象 - 尽管它的内容应该是相同的(即可比较的)。
我不得不说,当我阅读我的问题时,我认为它的措辞不好......所以我想我将包括我创建的课程的副本......
重要部分:
成员:挑战 - “结果集”类型对象的数组列表。
方法:runChallenge()
package KWhite;
/**
* the RScomparator is designed for the instance of comparing a double entry database system, as
* often occurs in localy run medical trials data.
*
* The double entry is to ensure that there are no errors made during input, the entry is performed
* in separate independant instances. The RScolmparator object is specifically able to take any
* number of result sets as its input (ie queries from multiple independantly created databases)
*
* It should be recognised that this object should probably be called as part of a DBcomparator
* object.
*
*/
//imports here
//import of logger class and required dependencies...
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.log4j.PropertyConfigurator;
import MrBlue.DB_Table;
import TawuaiLogger.tawuaiLogger;
public class RScomparator {
//Static variables
//the logger instance
private static final TawuaiLogger.tawuaiLogger errLog = new tawuaiLogger("RScomparator");
//class member variables
/** this is a selection of ResSet objects that are going to have thier data challenged */
private ArrayList<ResSet_KW> challenge;
/**the name of the current table being challenged*/
private String tableName;
/**a 'table' object for meta data reference purposes, this can be used for getting column types etc */
private DB_Table table;
//These are our report objects
/**a report array for challenge failures */
private ArrayList<report_KW> fail;
/**a report array for errors, ie no challenger able to be made, no equivalent value found */
private ArrayList<report_KW> errors;
/**a report array for the good values */
private ArrayList<report_KW> success;
/** this is either the main class or the constructor
*
* If it is a constructor rename to reflect the name of the class
* @param args
*/
public RScomparator(DB_Table t) //TODO add arguments as required
{
PropertyConfigurator.configure("Log4j.properties");
// TODO Auto-generated method stub
challenge = new ArrayList<ResSet_KW>();
//initialise our report objects for this challenge scenario
fail = new ArrayList<report_KW>();
errors = new ArrayList<report_KW>();
success = new ArrayList<report_KW>();
table = t;
tableName = t.getTblName();
}
//class methods go here
/**
* add a result set object into this comparator
*
* @param r the result set object being inserted into this challenge.
*
*/
public void addChallenger(ResSet_KW r)
{
this.challenge.add(r);
}
/**
* this runs the comparison process...
* Although no details in of itself are returned it calls other methods that do return a value
*
*/
public void runChallenge()
{
//TODO finish this method, creating a report object on the way
//these are the 2 result set objects that will be compared
ResSet_KW gold = new ResSet_KW ();
ResSet_KW silver = new ResSet_KW ();
//ensure the challenger list has objects in it.
if(challenge.size() < 2)
{
//it must have 2 objects..
errLog.add(3, "there are no results available for comparison of table " + this.tableName);
//either way we should create report object.
this.errors.add( new report_KW(tableName));
//break out of the method.
return;
}
//get the first row of data
gold = challenge.get(0);//the first result set.
//for each column in the result set, perform a search for the same key in the others..
for(HashMap<String, String> c : gold.getRS().keySet())
{//c is the key value in the map
//cycle over the challenge object
for (int i=1; i<challenge.size(); i++)//we don't want to use the first element, so start from 1 not zero
{
silver = challenge.get(i);
if (silver.hasKey(c))
{
//a temp object for meta data referencing
//only get the actual result values if there is a match
Column_KW a = gold.getRS().get(c);
Column_KW b = silver.getRS().get(c);
//make the comparison
a.compareTo(b, this.table);
//get the reports from the comparison
for(report_KW k :a.getFailure())
{
this.fail.add(k);
}
for(report_KW k :a.getPassed())
{
this.success.add(k);
}
for(report_KW k :a.getPassed())
{
this.errors.add(k);
}
}
else
{
break;//return to the next item in the for loop
}
}
}
}
/**
*a helper method to create the error message creator
*@ param m the extra message if any,
*@return s the full message
*/
private String getErrMessage(String m) {
//the third element in the current stact trace should be the calling method
StackTraceElement caller = Thread.currentThread().getStackTrace()[3];
String s = m + "\ncalled from line " + caller.getLineNumber()
+ "\nmethod: " + this.getClass() + "." + caller.getMethodName();
return s;
}
}//end class
附言。欢迎对我的代码发表任何评论或更多评论
提前致谢
大卫
编辑:我刚刚发现这个问题,嵌套映射或java中的组合键这将成为我的解决方案,创建一个'自定义'key_Index对象,然后为它定义一个hashcode()和equals对象。但是,我已经为我的 key_index 对象使用了“hashMap”,所以这会在我没有注意到的地方自动执行吗?