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使用XML作为持久存储介质的解决方案续

本文是"使XML作为持久存储介质的解决方案 "的续文.

上文中对成员的CRUD都采用同步进行资源保护,这种方案实际上是保护过度,带来的消极影响是降低了程序的效率,在下面的例子中,我们应该使用读写锁对资源进行保护.关于读写锁的分析请见"读写锁的OO分析(http://www.blogjava.net/sitinspring/archive/2007/10/21/154652.html)".

下面是代码:

MemberService类:
package com.sitinspring.model.service;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;

import org.apache.log4j.Logger;

import com.sitinspring.exception.PersistFileReadException;
import com.sitinspring.exception.PersistFileWriteException;
import com.sitinspring.model.domain.Member;
import com.sitinspring.model.domain.MemberFilter;
import com.sitinspring.model.persistence.Db4OPersistence;
import com.sitinspring.model.persistence.HibernatePersistence;
import com.sitinspring.model.persistence.Persistence;
import com.sitinspring.model.persistence.SqlPersistence;
import com.sitinspring.model.persistence.XmlPersistence;
import com.sitinspring.util.ReadWriteLock;

public class MemberService {
    
private static Logger logger = Logger.getLogger(MemberService.class);
    
    
private Persistence persistence;
    
private Persistence xmlPersistence;
    
private Persistence sqlPersistence;
    
private Persistence db4OPersistence;
    
private Persistence hibernatePersistence;

    
private Hashtable<String, Member> members;

    
private ReadWriteLock lock;

    
public MemberService() {
        members 
= new Hashtable<String, Member>();
        lock 
= new ReadWriteLock();                
    }

    
    
public void setPersistenceType(String type){
        logger.info(
"指定持久层为"+type);
        
        
if(type.equals("Xml")){                
            
if(xmlPersistence==null){
                
try{
                    xmlPersistence
=new XmlPersistence();
                }

                
catch(Exception ex){
                    logger.error(
"不能初始化XmlPersistence,原因:"+ex.getMessage());
                }
            
            }

            
            persistence
=xmlPersistence;                
        }
    
        
else if(type.equals("Sql")){
            
if(sqlPersistence==null){
                
try{
                    sqlPersistence
=new SqlPersistence();
                }

                
catch(Exception ex){
                    logger.error(
"不能初始化XmlPersistence,原因:"+ex.getMessage());
                }
            
            }

            
            persistence
=sqlPersistence;            
        }

        
else if(type.equals("Hibernate")){
            
if(hibernatePersistence==null){
                
try{
                    hibernatePersistence
=new HibernatePersistence();
                }

                
catch(Exception ex){
                    logger.error(
"不能初始化XmlPersistence,原因:"+ex.getMessage());
                }
            
            }

            
            persistence
=hibernatePersistence;            
        }

        
else{
            
if(db4OPersistence==null){
                
try{
                    db4OPersistence
=new Db4OPersistence();
                }

                
catch(Exception ex){
                    logger.error(
"不能初始化XmlPersistence,原因:"+ex.getMessage());
                }
            
            }

            
            persistence
=db4OPersistence;            
        }

        
        
try{
            members.clear();
            members
=persistence.loadMemberFromPersistence();
        }

        
catch(PersistFileReadException ex){
            logger.error(
""+persistence+"中读取失败");
        }

    }


    
public boolean hasMember(String name) {
        
return members.containsKey(name);
    }


    
public boolean hasMember(Member member) {
        
return hasMember(member.getName());
    }


    
public boolean add(Member member) throws PersistFileWriteException {
        
if (hasMember(member)) {
            System.out.println(
"Member:" + member.getName()
                    
+ " has been exist!");
            
return false;
        }
 else {
            
try {
                lock.writeLock();
                persistence.add(member);
                members.put(member.getName(), member);
                
return true;
            }
 finally {
                lock.writeUnlock();
            }

        }

    }


    
public boolean update(Member member) throws PersistFileWriteException {
        
if (hasMember(member)) {
            
try {
                lock.writeLock();

                persistence.update(member);

                Member oldMember 
= members.get(member.getName());
                oldMember.setTitle(member.getTitle());
                oldMember.setAge(member.getAge());

                
return true;
            }
 finally {
                lock.writeUnlock();
            }


        }
 else {
            System.out.println(
"Member:" + member.getName()
                    
+ " can't been found!");
            
return false;
        }

    }


    
public boolean saveOrUpdate(Member member) throws PersistFileWriteException {
        
if (hasMember(member)) {
            
return update(member);
        }
 else {
            
return add(member);
        }

    }


    
public boolean delete(Member member) throws PersistFileWriteException {
        
return delete(member.getName());
    }

    
    
public boolean delete(String memberName) throws PersistFileWriteException {
        
if (hasMember(memberName)) {
            
try {
                lock.writeLock();
                persistence.delete(memberName);
                members.remove(memberName);
                
return true;
            }
 finally {
                lock.writeUnlock();
            }

        }
 else {
            System.out.println(
"Member:" + memberName
                    
+ " can't been found!");
            
return false;
        }

    }


    @SuppressWarnings(
"unchecked")
    
public List<Member> search(MemberFilter memberFilter) {
        List
<Member> retval = new ArrayList<Member>();

        
try {
            lock.readLock();

            
for (Iterator it = members.keySet().iterator(); it.hasNext();) {
                String key 
= (String) it.next();
                Member member 
= members.get(key);

                
if (memberFilter.match(member)) {
                    retval.add(member);
                }

            }

        }
 finally {
            lock.readUnlock();
        }


        Collections.sort(retval);

        
return retval;
    }


    
public List<Member> getAll() {
        MemberFilter filter 
= new MemberFilter() {
            
public boolean match(Member member) {
                
return true;
            }

        }
;

        
return search(filter);
    }


    
public Member getMemberByName(String name) {
        
try {
            lock.readLock();
            
for (Iterator it = members.keySet().iterator(); it.hasNext();) {
                String key 
= (String) it.next();
                Member member 
= members.get(key);

                
if (member.getName().equals(name)) {
                    
return member;
                }

            }

        }
 finally {
            lock.readUnlock();
        }


        
return null;
    }


}

XmlPersistence类代码:
package com.sitinspring.model.persistence;

import java.io.File;
import java.io.FileWriter;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

import com.sitinspring.exception.PersistFileReadException;
import com.sitinspring.exception.PersistFileWriteException;
import com.sitinspring.model.domain.Member;
import com.sitinspring.util.FileDirUtil;

public class XmlPersistence extends Persistence {
    
private Document document;

    
public XmlPersistence() throws PersistFileReadException,
            PersistFileWriteException 
{
        filePos 
= "member.xml";

        
if (FileDirUtil.isFileExist(filePos) == false{
            
// Create document when file not exist
            createDocument();
            
return;
        }
 else {
            
// Get Docunent when file exist
            SAXReader reader = new SAXReader();

            
try {
                document 
= reader.read(new File(filePos));
            }
 catch (Exception ex) {
                
throw new PersistFileReadException(ex.getMessage());
            }

        }

    }

    
    
public String toString(){
        
return "XML存储介质,文件为:"+filePos;
    }


    
private void createDocument() throws PersistFileWriteException {
        String text 
= "<members></members>";

        
try {
            document 
= DocumentHelper.parseText(text);
            writeDocumentToFile();
        }
 catch (PersistFileWriteException ex) {
            
throw ex;
        }
 catch (Exception ex) {
            ex.printStackTrace();
        }

    }


    
private void writeDocumentToFile() throws PersistFileWriteException {
        
try {
            XMLWriter writer 
= new XMLWriter(new FileWriter(filePos));
            writer.write(document);
            writer.close();
        }
 catch (Exception ex) {
            
throw new PersistFileWriteException(ex.getMessage());
        }

    }


    
public Hashtable<String, Member> loadMemberFromPersistence()
            
throws PersistFileReadException {
        
try {
            Hashtable
<String, Member> retval = new Hashtable<String, Member>();

            List nodes 
= document.getRootElement().elements("member");

            
for (Iterator it = nodes.iterator(); it.hasNext();) {
                Element elm 
= (Element) it.next();
                Member member 
= new Member(elm.attributeValue("name"), elm
                        .elementText(
"age"), elm.elementText("title"));
                retval.put(member.getName(), member);
            }


            
return retval;
        }
 catch (Exception ex) {
            
throw new PersistFileReadException(ex.getMessage());
        }

    }


    
public boolean add(Member member) throws PersistFileWriteException {
        
try {
            Element rootElm 
= document.getRootElement();
            Element newMemberElm 
= rootElm.addElement("member");

            newMemberElm.addAttribute(
"name", member.getName());

            Element ageElm 
= newMemberElm.addElement("age");
            ageElm.setText(member.getAge());
            
            Element titleElm 
= newMemberElm.addElement("title");
            titleElm.setText(member.getTitle());

            writeDocumentToFile();

            
return true;
        }
 catch (PersistFileWriteException ex) {
            
throw ex;
        }

    }


    
public boolean update(Member member) throws PersistFileWriteException {
        
try {
            Element rootElm 
= document.getRootElement();
            List nodes 
= rootElm.elements("member");

            
for (Iterator it = nodes.iterator(); it.hasNext();) {
                Element elm 
= (Element) it.next();

                
if (elm.attributeValue("name").equals(member.getName())) {
                    elm.element(
"age").setText(member.getAge());
                    elm.element(
"title").setText(member.getTitle());
                    
break;
                }

            }


            writeDocumentToFile();

            
return false;
        }
 catch (PersistFileWriteException ex) {
            
throw ex;
        }

    }


    
public boolean delete(String name) throws PersistFileWriteException {
        
try {
            Element rootElm 
= document.getRootElement();
            List nodes 
= rootElm.elements("member");

            
for (Iterator it = nodes.iterator(); it.hasNext();) {
                Element elm 
= (Element) it.next();
                Member member 
= new Member(elm.attributeValue("name"), elm
                        .elementText(
"age"), elm.elementText("title"));

                
if (member.getName().equals(name)) {
                    rootElm.remove(elm);
                    
break;
                }

            }


            writeDocumentToFile();

            
return false;
        }
 catch (PersistFileWriteException ex) {
            
throw ex;
        }

    }


    
public boolean delete(Member member) throws PersistFileWriteException {
        
return delete(member.getName());
    }

}



posted on 2007-11-15 10:22 sitinspring 阅读(465) 评论(0)  编辑  收藏 所属分类: Object Orient Programming


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