Spring容器啓動後注入service到Servlet並自動執行

一般作法是定義一個Servlet，並在web.xml中配置Servlet的啓動順序<load-on-startup>的值在DispatcherServlet以後。但這樣作的缺點是在Servlet中沒法使用Spring的依賴注入功能，只能使用WebApplicationContext的getBean()方法獲取bean。

找到的解決辦法以下：

一、自定義一個用於代理啓動Servlet的類DelegatingServletProxy：

package cn.edu.swu.oa.common.util;

import java.io.IOException;

import javax.servlet.GenericServlet;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

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

public class DelegatingServletProxy extends GenericServlet {

	private String targetBean;
	private Servlet proxy;

	@Override
	public void service(ServletRequest arg0, ServletResponse arg1)
			throws ServletException, IOException {
		proxy.service(arg0, arg1);
	}

	@Override
	public void init() throws ServletException {
		this.targetBean = getServletName();
		getServletBean();
		proxy.init(getServletConfig());
	}

	private void getServletBean() {
		WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
		this.proxy = (Servlet)wac.getBean(targetBean);
	}

}

二、編寫啓動Servlet：

package cn.edu.swu.oa.common.util;

import java.io.IOException;
import java.util.List;

import javax.annotation.Resource;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;

import cn.edu.swu.oa.agency.model.Department;
import cn.edu.swu.oa.agency.model.Group;
import cn.edu.swu.oa.agency.service.DepService;
import cn.edu.swu.oa.agency.service.GroService;
import cn.edu.swu.oa.common.model.SysCode;
import cn.edu.swu.oa.safe.model.User;
import cn.edu.swu.oa.safe.service.UserService;

/**
 * 
 * 工程：WebOA
 * 類型解釋：Spring啓動完成後執行初始化操做
 * 類型表述：預讀某些實體的Key-Value，放入map，方便之後使用
 * @author ChenGuanwei
 * @version 建立時間：2010-3-25 下午10:55:44
 *
 */
@Component("initialServlet")
public class InitialServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	@Resource
	private UserService userService;

	@Resource
	private DepService depService;

	@Resource
	private GroService groService;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public InitialServlet() {
        super();
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

	@Override
	public void init(ServletConfig config) throws ServletException {
		//初始化eserMap
		List<User> users = userService.getUsers();
		for(int i = 0; i < users.size(); i++) {
			User user = users.get(i);
			Integer userId = user.getUserId();
			String userName = user.getUserName();
			SysCode.userMap.put(userId, userName);
		}
		//初始化depMap
		List<Department> deps = depService.getAllDeps();
		for(int i = 0; i < deps.size(); i++) {
			Department dep = deps.get(i);
			Integer depId = dep.getDepId();
			String depName = dep.getDepName();
			SysCode.depMap.put(depId, depName);
		}
		//初始化groMap
		List<Group> gros = groService.getAllGroups();
		for(int i = 0; i < gros.size(); i++) {
			Group gro = gros.get(i);
			Integer groId = gro.getGroId();
			String groName = gro.getGroName();
			SysCode.groMap.put(groId, groName);
		}
	}

}

在web.xml文件中配置InitialServlet ：

<servlet>
    <description></description>
    <display-name>InitialServlet</display-name>
    <servlet-name>initialServlet</servlet-name>
    <servlet-class>cn.edu.swu.oa.common.util.

DelegatingServletProxy

</servlet-class>
    <load-on-startup>2</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>initialServlet</servlet-name>
    <url-pattern>/InitialServlet</url-pattern>
  </servlet-mapping>

完成這些操做後，就能夠在Spring容器啓動後執行自定義的Servlet，而且在自定義Servlet中能夠使用Spring Annotation的自動注入功能。

備註：須要在xml裏面配置compont掃描：示例

<context:component-scan base-package="com.et59.cus"/>

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標籤:  servlet,  spring