问题描述：我自己写了一个jsp的表格用post请求访问Servlet，但是不管路径怎么写都不对，一直报404错误


 

 


     bug原因及解决方法：@WebServlet注解里的name属性对应着<servlet-name>，我只写了name，没有配置<url-pattern>（路径就对应于这个）,<url-pattern>对应的注解是urlpatterns或者value,value介意省略不写。所以修改@WebServlet里面的值就好了。


@WebServlet(name="Cservlet",urlpatterns="/CServlet");  //第一种写法，使用urlpatterns属性
@WebServlet("/CServlet")     //第二种写法，使用value属性

  更多字段可以去官网查询 https://docs.oracle.com/javaee/7/api/ 查找javax.servlet.annotation中的WebServletbin

刚做了一个登陆界面，用了WebServlet注解，发现验证码怎么也刷新不了，调试之后发现根本没有进入验证码生成的方法中去。这是我想肯定是注解或者XML文件出问题了。我用了原始的在XML文件中配置servlet.

<servlet>
<servlet-name>verifyCode</servlet-name>
<servlet-class>cn.sh.ideal.util.VerifyCode</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>verifyCode</servlet-name>
<url-pattern>/VerifyCode</url-pattern><!--这个和src的名字一样-->
</servlet-mapping>
然后取消生成验证码的注解
package cn.sh.ideal.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

//@WebServlet("/verifyCode")
public class VerifyCode extends HttpServlet {
	 
	private static final long serialVersionUID = 7819264488896491500L;
	
	private static Logger logger = Logger.getLogger(VerifyCode.class);

	protected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
		
		this.doPost(request, response);
	}

	protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
		 
		System.out.println("進來了");
		String data = "0123456789";
		 
		Random random = new Random();

		int width = 60;  
		
		int height = 30; 

		BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);

		Graphics2D g = (Graphics2D) image.getGraphics();

		g.setColor(Color.GREEN);

		g.fillRect(0, 0, width, height);

		g.setColor(Color.WHITE);

		g.fillRect(1, 1, width -1, height - 3);

		g.setFont(new Font("宋体", Font.PLAIN, 20));

		StringBuilder builder = new StringBuilder(); 

		for (int i = 0; i < 4; i++) {

			g.setColor(new Color(24, 88,129));

			int index = random.nextInt(data.length());
			
			String str = data.substring(index, index + 1);

			builder.append(str);
			
			g.rotate(Math.PI / 150, 1, 1);
			
			g.drawString(str, (i + 1) * (width / 5), 13);
		}
		
		//logger.info(builder.toString());

		request.getSession().setAttribute("identiCodeInSession",builder.toString());

		for (int i = 0; i < 5; i++) {

			g.setColor(new Color(random.nextInt(255), random.nextInt(255),random.nextInt(255)));

			g.drawLine(random.nextInt(width), random.nextInt(height),random.nextInt(width), random.nextInt(height));
		}
		
		response.setHeader("Pragma", "no-cache");    
		
		response.setHeader("Cache-Control", "no-cache"); 
		
		response.setDateHeader("Expires", 0);      

		ImageIO.write(image, "jpeg", response.getOutputStream());
 
	}

}
然后我发现可以，生成验证码。然后我发现tomcat6需要用这个，而注解这个方式需要用tomcat7.



注释web.xml文件中的servlet配置，然后取消@Webservlet注解的注释。发现可以完美生成验证码。

自定义注释 @WebFilterSort


实现源码: https://download.csdn.net/download/u013202238/12451011
编译后的jar包  http://download.csdn.net/detail/u013202238/9431110

使用demo, 创建三个Filter,分别为 MyFilter1,MyFilter2,MyFilter3,内容如下,分别指定Order为3、2、1

@WebFilterSort(order = 3)
public class MyFilter1 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println(MyFilter1.class.getName() + " init");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        System.out.println(MyFilter1.class.getName() + " before doFilter");

        filterChain.doFilter(servletRequest, servletResponse);

        System.out.println(MyFilter1.class.getName() + " after doFilter");

    }

    @Override
    public void destroy() {
        System.out.println(MyFilter1.class.getName() + " destroy");
    }
}


无论使用@javax.servlet.annotation.WebFilter或@WebFilterSort注解注册的Filter默认都在web.xml部署描述符中的过滤器加载后加载,可以使用isMatchAfter更改加载顺序


以url-pattern 过滤的最先执行,以servlet-name 过滤的在全部url-pattern执行后执行

在web.xml中设置参数

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

 <context-param>
     < description>被扫描的过滤器的所在包< /description>
     < param-name>filterPackage< /param-name>
     < param-value>com.test.filter.pack< /param-value>
 </context-param>

 <context-param>
     <description>是否扫描jar包中的类,默认为false不扫描</description>
     <param-name>filterInitScanJar</param-name>
     <param-value>false</param-value>
 </context-param>

 <context-param>
     <description>是否打印过滤器初始化信息(按排序顺序),默认false不打印,如果不打印可以不配置该参数</description>
     <param-name>filterInitDebug</param-name>
     <param-value>false</param-value>
 </context-param>

</web-app>

filterPackage  必填,包范围越小越好
filterInitScanJar 选填   是否扫描jar包中的类,默认为false不扫描
filterInitDebug 选填     是否打印过滤器初始化信息(按排序顺序),默认false不打印,如果不打印可以不配置该参数

 

在未指定排序时@WebFilter执行循序是按照被扫描到的循序执行的,



使用@WebFilterSort注解后,可以指定执行顺序,执行Filter






注解参数说明, 个参数等效于 @WebFilter中的参数

所需元素 
	
限定符和类型
			
必需的元素和说明
		
int
			
value (等同于order)
			
排序优先级
			
		
可选元素 
	
限定符和类型
			
可选元素和说明
		
boolean
			
asyncSupported
			
Declares whether the filter supports asynchronous operation mode.(默认false)
			
		
DispatcherType[]
			
dispatcherTypes
			
The dispatcher types to which the filter applies

			default {DispatcherType.REQUEST};
			
		
java.lang.String
			
displayName
			
The display name of the filter,默认值 ""
			
		
java.lang.String
			
filterName
			
The name of the filter,默认值 ""
			
		
boolean
			
isMatchAfter
			
表示该过滤器相对于部署描述符中过滤器的顺序 

			如果使用的参数为false,那么该过滤器映射将在部署描述符中描述的所有过滤器加载前进行加载, 

			如果为true( 默认 ),那么部署描述符中的过滤器将先被加载
			
		
java.lang.String[]
			
servletNames
			
The names of the servlets to which the filter applies.
			
		
java.lang.String[]
			
urlPatterns
			
The URL patterns to which the filter applies,default {"/*"}
			
		
 

 

今天再次用了下servlet3.1,我无论在类怎么写注解,发现没作用...这时找servlet3的规范了.终于找到我的问题的原因.
servlet3.1 final release:http://download.oracle.com/otndocs/jcp/servlet-3_1-fr-spec/index.html
第8章就说到注解与可插拔性.
In a web application, classes using annotations will have their annotations processed 

only if they are located in the WEB-INF/classes directory, or if they are packaged 

in a jar file located in WEB-INF/lib within the application. 
在web应用里,使用了注解的类,只有放到 WEB-INF/classes目录下或打成jar文件包放到WEB-INF/lib目录下才会处理它们的注解


.那放在其它地方就不会处理了???

1.做一下classes的windows快捷方式(这个相当于linux下的软链接),不管你成不成功,反正我没有成功!!!.不知linux成不成功,暂时没环境,不理.

2.再修改tomcat的conf/catalina.properties的shared.loader=,让tomcat加载这些类,反正是成功了!!!!


The web application deployment descriptor contains a new “metadata-complete” 

attribute on the web-app element. The “metadata-complete” attribute defines 

whether the web descriptor is complete, or whether the class files of the jar file 

should be examined for annotations and web fragments at deployment time. If 

“metadata-complete” is set to "true", the deployment tool MUST ignore any 

servlet annotations that specify deployment information present in the class files of 

the application and web fragments. If the metadata-complete attribute is not 

specified or is set to "false", the deployment tool must examine the class files of the 

application for annotations, and scan for web fragments.
web应用部署描述器(指的是web.xml)在web-app元素上包含了一个新的“metadata-complete” 属性,“metadata-complete” 属性是用来定义web描述器是不是完整的.
或者说是在部署的时候,类文件和jar文件是否要检验注解和片断(这个陌生).如果“metadata-complete” 设为"true",那部署工具一定会忽略......
如果“metadata-complete” 没有指定,或设为"false",部署工具必须检查应用的类文件注解和扫描web片断.


如果web.xml和注解都指定某个类为servlet会怎样呢,会冲突吗???狂汗.....
url-pattern不能相撞,否则tomcat死掉,启动都不让!!!!很容易理解哈....


因为我复制了tomcat examples下面的xml文件,metadata-complete也刚好是true.傻了吧.