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最新评论
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小小小羊:
好屌...
java.lang.NoClassDefFoundError: org/aspectj/weaver/reflect/ReflectionWorld$Refle -
liubinli2005:
这个可以脱底spring。单独使用吗?
DAO层:jade -
cangbaotu:
我觉得对于开发者来说,能脚本化编写爬虫是一件挺开心的事情( ̄▽ ...
网页爬取 -
asjava:
很好的文章, 但每段代码清单都重复了一次.
spring 事务 -
xia635317478:
jethypc 写道验证码的session无法传过去啊 还是我 ...
登陆验证码(struts2实现)
<context-param>与<init-param>的区别与作用
<context-param>的作用:
web.xml的配置中<context-param>配置作用
1. 启动一个WEB项目的时候,容器(如:Tomcat)会去读它的配置文件web.xml.读两个节点: <listener></listener> 和 <context-param></context-param>
web.xml的配置中<context-param>配置作用
1. 启动一个WEB项目的时候,容器(如:Tomcat)会去读它的配置文件web.xml.读两个节点: <listener></listener> 和 <context-param></context-param>
2.紧接着,容器创建一个ServletContext(上下文),这个WEB项目所有部分都将共享这个上下文.
3.容器将<context-param></context-param>转化为键值对,并交给ServletContext.
4.容器创建<listener></listener>中的类实例,即创建监听.
5.在监听中会有contextInitialized(ServletContextEvent args)初始化方法,在这个方法中获得ServletContext = ServletContextEvent.getServletContext();
context-param的值 = ServletContext.getInitParameter("context-param的键");
context-param的值 = ServletContext.getInitParameter("context-param的键");
6.得到这个context-param的值之后,你就可以做一些操作了.注意,这个时候你的WEB项目还没有完全启动完成.这个动作会比所有的Servlet都要早.
换句话说,这个时候,你对<context-param>中的键值做的操作,将在你的WEB项目完全启动之前被执行.
换句话说,这个时候,你对<context-param>中的键值做的操作,将在你的WEB项目完全启动之前被执行.
7.举例.你可能想在项目启动之前就打开数据库.
那么这里就可以在<context-param>中设置数据库的连接方式,在监听类中初始化数据库的连接.
那么这里就可以在<context-param>中设置数据库的连接方式,在监听类中初始化数据库的连接.
8.这个监听是自己写的一个类,除了初始化方法,它还有销毁方法.用于关闭应用前释放资源.比如说数据库连接的关闭.
如:
<!-- 加载spring的配置文件 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml,/WEB-INF/action-servlet.xml,/WEB-
<!-- 加载spring的配置文件 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml,/WEB-INF/action-servlet.xml,/WEB-
INF/jason-servlet.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
又如: --->自定义context-param,且自定义listener来获取这些信息
<context-param>
<param-name>urlrewrite</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>cluster</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>servletmapping</param-name>
<param-value>*.bbscs</param-value>
</context-param>
<context-param>
<param-name>poststoragemode</param-name>
<param-value>1</param-value>
</context-param>
<listener>
<listener-class>com.laoer.bbscs.web.servlet.SysListener</listener-class>
</listener>
<param-name>urlrewrite</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>cluster</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>servletmapping</param-name>
<param-value>*.bbscs</param-value>
</context-param>
<context-param>
<param-name>poststoragemode</param-name>
<param-value>1</param-value>
</context-param>
<listener>
<listener-class>com.laoer.bbscs.web.servlet.SysListener</listener-class>
</listener>
public class SysListener extends HttpServlet implements ServletContextListener {
private static final Log logger = LogFactory.getLog(SysListener.class);
public void contextDestroyed(ServletContextEvent sce) {
//用于在容器关闭时,操作
}
}
//用于在容器开启时,操作
public void contextInitialized(ServletContextEvent sce) {
String rootpath = sce.getServletContext().getRealPath("/");
System.out.println("-------------rootPath:"+rootpath);
String rootpath = sce.getServletContext().getRealPath("/");
System.out.println("-------------rootPath:"+rootpath);
if (rootpath != null) {
rootpath = rootpath.replaceAll("\\\\", "/");
} else {
rootpath = "/";
}
if (!rootpath.endsWith("/")) {
rootpath = rootpath + "/";
}
Constant.ROOTPATH = rootpath;
logger.info("Application Run Path:" + rootpath);
String urlrewrtie = sce.getServletContext().getInitParameter("urlrewrite");
boolean burlrewrtie = false;
if (urlrewrtie != null) {
burlrewrtie = Boolean.parseBoolean(urlrewrtie);
}
Constant.USE_URL_REWRITE = burlrewrtie;
logger.info("Use Urlrewrite:" + burlrewrtie);
其它略之....
rootpath = rootpath.replaceAll("\\\\", "/");
} else {
rootpath = "/";
}
if (!rootpath.endsWith("/")) {
rootpath = rootpath + "/";
}
Constant.ROOTPATH = rootpath;
logger.info("Application Run Path:" + rootpath);
String urlrewrtie = sce.getServletContext().getInitParameter("urlrewrite");
boolean burlrewrtie = false;
if (urlrewrtie != null) {
burlrewrtie = Boolean.parseBoolean(urlrewrtie);
}
Constant.USE_URL_REWRITE = burlrewrtie;
logger.info("Use Urlrewrite:" + burlrewrtie);
其它略之....
}
}
/*最终输出
-------------rootPath:D:\tomcat_bbs\webapps\BBSCS_8_0_3\
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
/*最终输出
-------------rootPath:D:\tomcat_bbs\webapps\BBSCS_8_0_3\
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
Application Run Path:D:/tomcat_bbs/webapps/BBSCS_8_0_3/
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
Use Urlrewrite:true
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
Use Cluster:false
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,526 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
SERVLET MAPPING:*.bbscs
2009-06-09 21:51:46,573 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
2009-06-09 21:51:46,573 [com.laoer.bbscs.web.servlet.SysListener]-[INFO]
Post Storage Mode:1
*/
*/
context-param和init-param区别
web.xml里面可以定义两种参数:
(1)application范围内的参数,存放在servletcontext中,在web.xml中配置如下:
<context-param>
<param-name>context/param</param-name>
<param-value>avalible during application</param-value>
</context-param>
web.xml里面可以定义两种参数:
(1)application范围内的参数,存放在servletcontext中,在web.xml中配置如下:
<context-param>
<param-name>context/param</param-name>
<param-value>avalible during application</param-value>
</context-param>
(2)servlet范围内的参数,只能在servlet的init()方法中取得,在web.xml中配置如下:
<servlet>
<servlet-name>MainServlet</servlet-name>
<servlet-class>com.wes.controller.MainServlet</servlet-class>
<init-param>
<param-name>param1</param-name>
<param-value>avalible in servlet init()</param-value>
</init-param>
<load-on-startup>0</load-on-startup>
</servlet>
<servlet>
<servlet-name>MainServlet</servlet-name>
<servlet-class>com.wes.controller.MainServlet</servlet-class>
<init-param>
<param-name>param1</param-name>
<param-value>avalible in servlet init()</param-value>
</init-param>
<load-on-startup>0</load-on-startup>
</servlet>
在servlet中可以通过代码分别取用:
package com.wes.controller;
package com.wes.controller;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServlet;
public class MainServlet extends HttpServlet ...{
public MainServlet() ...{
super();
}
public void init() throws ServletException ...{
System.out.println("下面的两个参数param1是在servlet中存放的");
System.out.println(this.getInitParameter("param1"));
System.out.println("下面的参数是存放在servletcontext中的");
System.out.println(getServletContext().getInitParameter("context/param"));
}
}
super();
}
public void init() throws ServletException ...{
System.out.println("下面的两个参数param1是在servlet中存放的");
System.out.println(this.getInitParameter("param1"));
System.out.println("下面的参数是存放在servletcontext中的");
System.out.println(getServletContext().getInitParameter("context/param"));
}
}
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web.xml 中的listener、 filter、servlet 加载顺序及其详解
2013-09-11 18:28 901web.xml 中的listener、 filter、serv ... -
Jsp内建对象详解
2013-08-09 22:19 1042Jsp内建对象详解 方法: 1. void ... -
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
2013-06-15 09:01 5094JSP页面头部的标识:<!DOCTYPE HTML PU ... -
购物车实现的三种方式
2013-03-31 10:33 1016购物车3种实现方式 详 ... -
Servlet3.0-使用注解定义Servlet
2013-03-26 18:03 983http://www.cnblogs.com/luxh/arc ... -
将Web应用打包成.war
2012-12-26 15:32 1457如何将Web应用打包成.war ... -
Servlet详解
2012-12-12 09:21 843Servlet详解 参考: http://my.oschin ... -
JSTL(JSP标准标签库)
2012-11-03 21:20 776JSTL( JSP标准标签库 ) JSTL(JSP Stan ... -
JNDI(Java命名和目录接口)
2012-11-03 14:20 796JNDI(Java命名和目录接口) JNDI(Java N ... -
Server.xml <Context/>详解
2012-10-29 14:09 14560Tomcat中server.xml配置及Context的配置s ... -
JSP/Servlet总结
2012-10-29 17:01 895JSP/Servlet总结 1.Request ... -
Servlet生命周期
2012-10-28 21:10 736Servlet生命周期 1.加载、实例化:请求到来时web容 ... -
post和get请求方式的区别
2012-10-28 20:54 927post和get请求方式的区别 ... -
Dom4j读取XML
2012-10-26 20:38 864http://www.blogjava.net/biiau/a ... -
POJO 和 DTO
2012-10-10 17:19 1105POJO和DTO POJO( ... -
jsp两种包含
2012-10-02 10:49 956jsp两种包含 1.静态包含 <%@include f ... -
javabean一(转)
2012-09-19 08:17 993javabean一 32.1 Introductio ... -
登陆验证码(Servlet实现)
2012-09-14 22:27 7339登陆验证码(Servlet实现) 1.前台登陆界面: &l ...
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