写一个BeanFactory来管理Service使Service和Dao都单例

1.原来的项目

2.优化的思想：

项目目录：

1.Dao

2.Service

import cn.oracle.books.dao.IBookDao;

import cn.oracle.domain.Book;

publicclassBookService implements IBookService {

    //private BookDaodao = new BookDao();

    private IBookDaodao ;

    publicvoid setDao(IBookDao dao) {

        this.dao = dao;

    }

    public List<Book>query(String typeid) {

        returndao.query(typeid);

    }

    public Book load(Stringbookid) {

        returndao.load(bookid);

    }

}

3.Servlet

4.   BeanFactory

import org.apache.commons.beanutils.BeanUtils;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

import cn.oracle.books.service.IBookService;

import cn.oracle.domain.Book;

publicclassBeanFactory {

   //声明一个map<id,object>

    privatestaticMap<String,Object> map =newHashMap<String,Object>();

   static{

    try {

       //获取文件的目录

            Stringpath = BeanFactory.class.getClassLoader().getResource("beans.xml").getPath();

            System.err.println("path is:"+path);

            //解析这个xml文件

            Filefile = newFile(path);

            if(!file.exists()){

                thrownew RuntimeException("文件不存在");

            }

            SAXReadersax = newSAXReader();

            Documentdom = sax.read(file);

            List<Element>list = dom.selectNodes("//bean");

            //把独到的id放到map并把这个类实例化

            for (Element el : list) {

                Stringid = el.attributeValue("id");

                Stringcls = el.attributeValue("class");

                Objectobj = Class.forName(cls).newInstance();

                map.put(id, obj);

                //再判断是否存在property这样的子元素

                List<Element>props =el.elements("property");

                if(props!=null &&props.size()>0){

                   for (Element p : props) {

                       Stringname = p.attributeValue("name");

                       Stringref = p.attributeValue("ref");//ref是bookDao（BookDao的id）

                       //获取放到map中的对象

                       Objectval = map.get(ref);

                       if(val==null){

                           load(dom,ref);

                           val= map.get(ref);

                       }

                       //干的是：setDao(IBookDaodao)

                       BeanUtils.setProperty(obj,name, val);//obj是BookService,name是dao,val是BookDao

                   }

                }

            }

      

        }catch(Exception e) {

            thrownew RuntimeException(e);

        }

   }

   publicstaticObject getBean(String id){

       returnmap.get(id);

   }

   publicstaticvoidload(Document dom,String beanid)throws Exception{

       Elementel = (Element) dom.selectSingleNode("//bean[@id='"+beanid+"']");

       Stringid = el.attributeValue("id");

       Stringcls = el.attributeValue("class");

       Objectobj = Class.forName(cls).newInstance();

       map.put(id, obj);

   

   }

}

5.beans.xml

<?xmlversion="1.0"encoding="UTF-8"?>

<beans>

   <!-- 声明BooksDao的实例 -->

   <beanid="bookDao"class="cn.oracle.books.dao.BookDao">

   </bean>

   <beanid="bookService"class="cn.oracle.books.service.BookService">

        <propertyname="dao"ref="bookDao"/>

   </bean>

</beans>