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

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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;
    }

}
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

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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 {

 @Resource
 private TdFeedingRatesDAO tdFeedingRatesDAO ;
 @Resource
 private TdProductFishDAO tdProductFishDAO;

 public GetDictionaryInfo(){
 super();
 }
 private static WebApplicationContext springContext;
 public static ServletContext _servletContext;//这个是为了取servletContext
 private 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;
 }

}
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 {

@Resource
private TdFeedingRatesDAO tdFeedingRatesDAO ;
@Resource
private TdProductFishDAO tdProductFishDAO;

public GetDictionaryInfo(){
 super();
}
private static WebApplicationContext springContext;
public static ServletContext _servletContext;//这个是为了取servletContext
private 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

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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. 
 *
 * @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 here

 springContext = 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. 
 */
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

 /**
 * The doGet method of the servlet. 
 *
 * 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. 
 *
 * 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();
 }

}
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. 
*
* @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 here

 springContext = 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. 
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet. 
*
* 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. 
*
* 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

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

<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

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

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

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GetDictionaryInfo.getInstance().reloadDictionaryInfoMap();
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

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

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%%%%%%%%%%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 12
Hibernate: 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-8080
2010-4-6 9:35:38 org.apache.jk.common.ChannelSocket init
信息: JK: ajp13 listening on /0.0.0.0:8009
2010-4-6 9:35:38 org.apache.jk.server.JkMain start
信息: Jk running ID=0 time=0/31 config=null
2010-4-6 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 12
Hibernate: 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