spring学习笔记--在自定义servlet中获取到spring的applicationcontext

需要做一个参数初始化类，当web应用被加载时从数据库里取出相关的参数设置

，并把这些参数放置到application里，jsp页面可以从中取出。

1.在web.xml中配置：

<servlet>

<servlet-name>Dispatcher</servlet-name>

<servlet-

class>org.springframework.web.servlet.DispatcherServlet</servlet-

class>

<init-param>

<param-name>contextConfigLocation</param-name>

<param-value>/WEB-INF/Dispatcher-

servlet.xml,/WEB-INF/applicationContext.xml</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet>

<servlet-name>context</servlet-name>

<servlet-

class>org.springframework.web.context.ContextLoaderServlet</servlet-

class>

<load-on-startup>2</load-on-startup>

</servlet>

<servlet>

<servlet-name>InitialServlet</servlet-name>

<servlet-

class>com.anylinks.billreturn.Web.InitialServlet</servlet-class>

<load-on-startup>3</load-on-startup>

</servlet>

2.servlet代码

package com.anylinks.billreturn.Web;

import java.util.Collection;

import java.util.Iterator;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import com.anylinks.billreturn.BO.SysParameter;

import com.anylinks.billreturn.Service.ISysParameterService;

/*

* 初始化Servlet，从数据库中读取参数表，保存在application里

*/

public class InitialServlet extends HttpServlet {

private Log log = LogFactory.getLog(this.getClass());

private ISysParameterService sysParameterService;

/**

* 从数据库中读取参数表，保存在application里

*

* @throws ServletException

* if an error occure

*/

public void init() throws ServletException {

log.debug("start to intitail ");

// 获取WebApplicationContext

ServletContext application = getServletContext();

WebApplicationContext wac = WebApplicationContextUtils

.getWebApplicationContext

(application);

// 调用sysParameterService取出所有的系统参数

sysParameterService = (ISysParameterService) wac

.getBean("sysParameterService");

Collection paras =

sysParameterService.findAllParameters();

log.debug("sys parameters size:" + paras.size());

// 把参数加到application里去

for (Iterator iter = paras.iterator(); iter.hasNext

();) {

SysParameter para = (SysParameter) iter.next

();

application.setAttribute(para.getParaName(),

para.getParaValue());

log.debug("initial parameter: key=" +

para.getParaName()

+ ", value=" +

para.getParaValue());

}

}

}

需要注意的地方：

1.仅仅配置一个DispatcherServlet是不够的，我开始就是这样，然后再servlet

里面怎么取都取不到WebApplicationContext 。配置上

org.springframework.web.context.ContextLoaderServlet之后才能取的到

WebApplicationContext 。

2.注意一下<load-on-startup>3</load-on-startup>，因为用到spring的

hibernateDaoSupport,所以必须在spring加载完之后再加载InitialServlet.