【原创】SSH开发框架中，实现系统启动加载类，读取数据库常用数据进入内存，利用Spring托管，并完成reload功能

各位看官，请做好心理准备，这个帖子会很长，因为小弟已经做好写很长的准备。

 

现在说一下需求，这次的项目是做一个水产养殖相关的项目，系统开启以后很多地方要用到数据库里的字典数据，比如部门表，养殖对象表，这些数据是可变的，但是变化频率很小，所有每次用到的时候都去数据库取数据很明显的是对资源的浪费，所以想按照以前的方法把数据从数据库里读取出来，放到内存，每次用到的时候直接去内存找就可以了。想法应该是正确的，可是用到了SSH框架，做起来就有点小困难了，研究了一下午，总是是搞定。思路和代码写出来，有错误的地方请大家指正。

 

正式开始！中间的调错过程省去，直接如何实现。

 

         另配一个listener,和spring同时启动，不可取。因为listener的启动机制貌似是线程，并不是按顺序一个一个启动，所有想到直接在spring的配置文件里，注册bean文件，让bean文件来执行取数据的工作，但是这个bean显然是不能使用DAO的类，因为DAO层的东西无法注入进来，所以要有个替代的东西，这个东西好难找啊，就是BeanPostProcessor接口，用类PBSTrackManagerPostProcessor实现它其中的一个方法postProcessAfterInitialization，这个方法里可以引入一个类GetDictionaryInfo，实现类的方法getAllInfo()，当getAllInfo去调用DAO层的数据时就可以了。

不说了，直接上源码：

PBSTrackManagerPostProcessor.java

import org.springframework.beans.BeansException;import org.springframework.beans.factory.config.BeanPostProcessor;/** * @author ROC * @2010年4月5日18:24:58 * 实现BeanPostProcessor接口，可以实现在Spring加载时，调取一个的对象的方法，使其能够取得实例化以后的DAO. * * * * */public class PBSTrackManagerPostProcessor implements BeanPostProcessor { public Object postProcessAfterInitialization(Object obj, String s) throws BeansException { if(obj instanceof GetDictionaryInfo)//GetDictionaryInfo为类名 { ((GetDictionaryInfo) obj).getAllInfo();//getAllInfo为GetDictionaryInfo的方法 } return obj; } public Object postProcessBeforeInitialization(Object obj, String s) throws BeansException { return obj; }}

 

GetDictionaryInfo.java

import java.util.HashMap;import javax.annotation.Resource;import javax.servlet.ServletContext;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;import java.util.ArrayList;import edu.ldu.system.preferences.feeding.DAO.TdFeedingRatesDAO;import edu.ldu.system.preferences.product.DAO.TdProductFishDAO;/** * @author ROC * 2010年4月5日18:26:55 * 实现getAllInfo方法，取得所有常用字典表里的数据 * * */public class GetDictionaryInfo {@Resourceprivate TdFeedingRatesDAO tdFeedingRatesDAO ;@Resourceprivate TdProductFishDAO tdProductFishDAO;public GetDictionaryInfo(){super();}private static WebApplicationContext springContext;public static ServletContext _servletContext;//这个是为了取servletContextprivate static GetDictionaryInfo _instance;public static GetDictionaryInfo getInstance(){springContext = WebApplicationContextUtils.getWebApplicationContext(_servletContext);if(null == _instance)_instance = (GetDictionaryInfo)springContext.getBean("getDictionaryInfo");return _instance;}public static HashMap<String,ArrayList> dictionaryInfoMap = new HashMap<String, ArrayList>();public void getAllInfo() {System.out.println("%%%%%%%%%%系统启动加载......");System.out.println("@@@@@@@@@@开始从数据库中取数据！");ArrayList tdFeedingRatesList = (ArrayList)tdFeedingRatesDAO.findAll();System.out.println("数据LIST - 1 的大小 "+tdFeedingRatesList.size());ArrayList tdProductFishList = (ArrayList)tdProductFishDAO.findAll();System.out.println("数据LIST - 2 的大小 "+tdProductFishList.size());System.out.println("@@@@@@@@@@数据从数据库中全部取出！");dictionaryInfoMap.put("tdFeedingRatesList", tdFeedingRatesList);dictionaryInfoMap.put("tdProductFishList", tdProductFishList);System.out.println("@@@@@@@@@@数据打包完毕，全部放进了dictionaryInfoMap！");}/** * 重新加载字典表数据！ * */public void reloadDictionaryInfoMap(){System.out.println("==========~~~~~~~~~~系统开始重新加载字典表");dictionaryInfoMap.clear();System.out.println("==========~~~~~~~~~~字典表MAP,清空成功！");getAllInfo();System.out.println("==========~~~~~~~~~~重新加载字典表成功");}public HashMap<String, ArrayList> getDictionaryInfoMap() {return dictionaryInfoMap;}public void setDictionaryInfoMap(HashMap<String, ArrayList> dictionaryInfoMap) {this.dictionaryInfoMap = dictionaryInfoMap;}}

 

 

然后这个GetDictionaryInfo.java是个普通的类，所有要有一个servlet启动并且把取得HaspMap放到context里去

 

MainServlet.java

 

import java.io.IOException;import java.io.PrintWriter;import java.util.HashMap;import java.util.ArrayList;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;public class MainServlet extends HttpServlet {/** * Initialization of the servlet. <br> * * @throws ServletException * if an error occurs */private static final long serialVersionUID = 1L;// private SystemParamServicesImpl sysParamService;private static WebApplicationContext springContext;private ServletContext context;public void init() throws ServletException {// Put your code herespringContext = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());GetDictionaryInfo._servletContext=this.getServletContext();context = this.getServletContext();// GetDictionaryInfo getDictionaryInfo = new GetDictionaryInfo();HashMap<String, ArrayList> dictionaryInfoMap = (HashMap<String, ArrayList>) GetDictionaryInfo.dictionaryInfoMap;System.out.println("字典MAP里的数据长度为" + dictionaryInfoMap.size() + "个");context.setAttribute("dictionaryInfoMap", dictionaryInfoMap);System.out.println("@@@@@@@@@@系统字典表数据加载成功！");}/** * Constructor of the object. */public MainServlet() {super();}/** * Destruction of the servlet. <br> */public void destroy() {super.destroy(); // Just puts "destroy" string in log// Put your code here}/** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("<!DOCTYPE HTML PUBLIC /"-//W3C//DTD HTML 4.01 Transitional//EN/">");out.println("<HTML>");out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");out.println(" <BODY>");out.print(" This is ");out.print(this.getClass());out.println(", using the GET method");out.println(" </BODY>");out.println("</HTML>");out.flush();out.close();}/** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to * post. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("<!DOCTYPE HTML PUBLIC /"-//W3C//DTD HTML 4.01 Transitional//EN/">");out.println("<HTML>");out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");out.println(" <BODY>");out.print(" This is ");out.print(this.getClass());out.println(", using the POST method");out.println(" </BODY>");out.println("</HTML>");out.flush();out.close();}}

 

 

然后完成注册功能

applicationContext.XML

 

<!-- 调用GetDictionaryInfo 读的 --><bean id="pbsTrackManagerPostProcess" class="edu.ldu.utils.PBSTrackManagerPostProcessor" /><bean id="getDictionaryInfo" class="edu.ldu.utils.GetDictionaryInfo" />

 

配置web.xml让MainServlet.java自启动

 

<servlet><servlet-name>MainServlet</servlet-name><servlet-class>edu.ldu.utils.MainServlet</servlet-class><load-on-startup>1</load-on-startup></servlet>

 

 

然后就是如何在Action里取到数据了：

 

ServletContext context = ServletActionContext.getServletContext();HashMap dictionaryInfoMap = (HashMap)context.getAttribute("dictionaryInfoMap");

 

 

 

又一个问题就是解决触发一个函数，让这些东西重新加载。

 

GetDictionaryInfo.getInstance().reloadDictionaryInfoMap();

 

 

reloadDictionaryInfoMap();实现起来时比较困难的，要在GetDictionaryInfo 取到ServletContext，而且要必须取到第一次实例的GetDictionaryInfo ，所有有一个东西很好用，就是Spring的context,取到他的方式

private static WebApplicationContext springContext;springContext = WebApplicationContextUtils.getWebApplicationContext(_servletContext);

 

 

 

 

这样就大功告成，跑起来以后的结果，列出控制台的输出数据：

%%%%%%%%%%系统启动加载......@@@@@@@@@@开始从数据库中取数据！Hibernate: select tdfeedingr0_.pk_id as pk1_0_, tdfeedingr0_.fishTypeId as fishTypeId0_, tdfeedingr0_.waterTemperature as waterTem3_0_, tdfeedingr0_.growthStageId as growthSt4_0_, tdfeedingr0_.baitId as baitId0_, tdfeedingr0_.feedingRate as feedingR6_0_, tdfeedingr0_.state as state0_ from LDU_Aquaculture.dbo.td_feeding_rates tdfeedingr0_数据LIST - 1 的大小 12Hibernate: select tdproductf0_.pk_fishid as pk1_7_, tdproductf0_.fishname as fishname7_, tdproductf0_.fish_store as fish3_7_, tdproductf0_.state as state7_, tdproductf0_.creationDate as creation5_7_, tdproductf0_.lastModifiedDate as lastModi6_7_ from LDU_Aquaculture.dbo.td_product_fish tdproductf0_数据LIST - 2 的大小 2@@@@@@@@@@数据从数据库中全部取出！@@@@@@@@@@数据打包完毕，全部放进了dictionaryInfoMap！字典MAP里的数据长度为2个@@@@@@@@@@系统字典表数据加载成功！系统启动，开始装载日志文件……DEBUG日志文件路径为：E:/Program Files/Tomcat 6.0/webapps/Aquaculture/WEB-INF/logs/app-debug.log INFO日志文件路径为：E:/Program Files/Tomcat 6.0/webapps/Aquaculture/WEB-INF/logs/app-info.log WARN日志文件路径为：E:/Program Files/Tomcat 6.0/webapps/Aquaculture/WEB-INF/logs/app-warn.log ERROR日志文件路径为：E:/Program Files/Tomcat 6.0/webapps/Aquaculture/WEB-INF/logs/app-error.log 2010-4-6 9:35:38 org.apache.coyote.http11.Http11Protocol start信息: Starting Coyote HTTP/1.1 on http-80802010-4-6 9:35:38 org.apache.jk.common.ChannelSocket init信息: JK: ajp13 listening on /0.0.0.0:80092010-4-6 9:35:38 org.apache.jk.server.JkMain start信息: Jk running ID=0 time=0/31 config=null2010-4-6 9:35:38 org.apache.catalina.startup.Catalina start信息: Server startup in 10921 ms==========~~~~~~~~~~系统开始重新加载字典表==========~~~~~~~~~~字典表MAP,清空成功！%%%%%%%%%%系统启动加载......@@@@@@@@@@开始从数据库中取数据！Hibernate: select tdfeedingr0_.pk_id as pk1_0_, tdfeedingr0_.fishTypeId as fishTypeId0_, tdfeedingr0_.waterTemperature as waterTem3_0_, tdfeedingr0_.growthStageId as growthSt4_0_, tdfeedingr0_.baitId as baitId0_, tdfeedingr0_.feedingRate as feedingR6_0_, tdfeedingr0_.state as state0_ from LDU_Aquaculture.dbo.td_feeding_rates tdfeedingr0_数据LIST - 1 的大小 12Hibernate: select tdproductf0_.pk_fishid as pk1_7_, tdproductf0_.fishname as fishname7_, tdproductf0_.fish_store as fish3_7_, tdproductf0_.state as state7_, tdproductf0_.creationDate as creation5_7_, tdproductf0_.lastModifiedDate as lastModi6_7_ from LDU_Aquaculture.dbo.td_product_fish tdproductf0_数据LIST - 2 的大小 2@@@@@@@@@@数据从数据库中全部取出！@@@@@@@@@@数据打包完毕，全部放进了dictionaryInfoMap！==========~~~~~~~~~~重新加载字典表成功

 

 

终于写完，请大家指正。