html - Servlet returns "HTTP Status 404 The requested resource (/servlet) is not available" -

i have html form in jsp file in webcontent/jsps folder. have servlet class servlet.java in default package in src folder. in web.xml mapped /servlet.

i have tried several urls in action attribute of html form:

<form action="/servlet">

<form action="/servlet.java">

<form action="/src/servlet.java">

<form action="../servlet.java">

but none of work. keep returning http 404 error below in tomcat 6/7/8:

http status 404 — /servlet

description: requested resource (/servlet) not available.

or below in tomcat 8.5/9:

http status 404 — not found

message: /servlet

description: origin server did not find current representation target resource or not willing disclose 1 exists

why not working?

put servlet class in `package`

first of all, put servlet class in java package. should always put publicly reuseable java classes in package, otherwise invisible classes in package, such server itself. way eliminiate potential environment-specific problems. packageless servlets work in specific tomcat+jdk combinations , should never relied upon.

in case of "plain" ide project, class needs placed in package structure inside "java resources" folder , not "webcontent", web files such jsp. below example of folder structure of default eclipse dynamic web project seen in navigator view:

eclipseprojectname  |-- src  |    `-- com  |         `-- example  |              `-- yourservlet.java  |-- webcontent  |    |-- web-inf  |    |    `-- web.xml  |    `-- jsps  |         `-- page.jsp  :

in case of maven project, class needs placed in package structure inside main/java and not e.g. main/resources, non-class files. below example of folder structure of default maven webapp project seen in eclipse's navigator view:

mavenprojectname  |-- src  |    `-- main  |         |-- java  |         |    `-- com  |         |         `-- example  |         |              `-- yourservlet.java  |         |-- resources  |         `-- webapp  |              |-- web-inf  |              |    `-- web.xml  |              `-- jsps  |                   `-- page.jsp  :

note /jsps subfolder not strictly necessary. can without , put jsp file directly in webcontent/webapp root, i'm taking on question.

set servlet url in `url-pattern`

the servlet url specified "url pattern" of servlet mapping. it's absolutely not per definition classname/filename of servlet class. url pattern specified value of @webservlet annotation.

package com.example; // use package!  @webservlet("/servlet") // url of servlet. public class yourservlet extends httpservlet { // must public , extend httpservlet.     // ... }

in case want support path parameters /servlet/foo/bar, use url pattern of /servlet/* instead. see servlet , path parameters /xyz/{value}/test, how map in web.xml?

`@webservlet` works on servlet 3.0 or newer

in order use @webservlet, need make sure web.xml file, if (it's optional since servlet 3.0), declared conform servlet 3.0+ version and not conform e.g. 2.5 version or lower. below servlet 3.1 compatible 1 (which matches tomcat 8+, wildfly 8+, glassfish 4+, etc).

<?xml version="1.0" encoding="utf-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance"     xmlns="http://xmlns.jcp.org/xml/ns/javaee"     xsi:schemalocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"     id="webapp_id" version="3.1" >     <!-- config here. --> </web-app>

or, in case you're not on servlet 3.0+ yet (not tomcat 7 or newer, tomcat 6 or older), remove @webservlet annotation.

package com.example;  public class yourservlet extends httpservlet {     // ... }

and register servlet instead in web.xml this:

<servlet>     <servlet-name>yourservlet</servlet-name>     <servlet-class>com.example.yourservlet</servlet-class> </servlet> <servlet-mapping>     <servlet-name>yourservlet</servlet-name>     <url-pattern>/servlet</url-pattern>  <!-- url of servlet. --> </servlet-mapping>

note should not use both ways. use either annotation based configuarion or xml based configuration.

verifying build/deployment

in case you're using build tool such eclipse and/or maven, need make absolutely sure compiled servlet class file resides in package structure in /web-inf/classes folder of produced war file. in case of package com.example; public class yourservlet, must located in /web-inf/classes/com/example/yourservlet.class. otherwise face in case of @webservlet 404 error, or in case of <servlet> http 500 error below:

http status 500

error instantiating servlet class com.example.yourservlet

and find in server log java.lang.classnotfoundexception: com.example.yourservlet, followed java.lang.noclassdeffounderror: com.example.yourservlet, in turn followed javax.servlet.servletexception: error instantiating servlet class com.example.yourservlet.

an easy way verify if servlet correctly compiled , placed in classpath let build tool produce war file (e.g. rightclick project, export > war file in eclipse) , inspect contents zip tool. if servlet class missing in /web-inf/classes, project badly configured or ide/project configuration defaults have been mistakenly reverted (e.g. project > build automatically has been disabled in eclipse). in case have no clue, best restart scratch , not touch ide/project configuration defaults.

testing servlet individually

provided server runs on localhost:8080, , war deployed on context path of /contextname (which defaults ide project name, case sensitive!), , servlet hasn't failed initialization (read server logs deploy/servlet success/fail messages , actual context path , servlet mapping), servlet url pattern of /servlet available @ http://localhost:8080/contextname/servlet.

you can enter straight in browser's address bar test invidivually. if doget() overriden , implemented, see output in browser. or if don't have doget() or if incorrectly calls super.doget(), "http 405: http method not supported url" error shown (which still better 404 405 evidence servlet found).

overriding service() bad practice, unless you're reinventing mvc framework — unlikely if you're starting out servlets , clueless problem described in current question ;) see design patterns web based applications.

regardless, if servlet returns 404 when tested invidivually, it's entirely pointless try html form instead. logically, it's therefore entirely pointless include html form in questions 404 errors servlet.

referencing servlet url html

once you've verified servlet works fine when invoked individually, can advance html. concrete problem html form, <form action> value needs valid url. same applies <a href>. need understand how absolute/relative urls work. know, url web address can enter/see in webbrowser's address bar. if you're specifying relative url form action, i.e. without http:// scheme, becomes relative current url see in webbrowser's address bar. it's absolutely not relative jsp/html file location in server's war folder structure many starters seem think.

so, assuming jsp page html form opened http://localhost:8080/contextname/jsps/page.jsp, , need submit servlet located in http://localhost:8080/contextname/servlet, here several cases (note can safely substitute <form action> <a href> here):

form action submits url leading slash.
```
<form action="/servlet"> 
```
the leading slash / makes url relative domain, form submit to
```
http://localhost:8080/servlet 
```
but result in 404 it's in wrong context.
form action submits url without leading slash.
```
<form action="servlet"> 
```
this makes url relative current folder of current url, form submit to
```
http://localhost:8080/contextname/jsps/servlet 
```
but result in 404 it's in wrong folder.
form action submits url goes 1 folder up.
```
<form action="../servlet"> 
```
this go 1 folder (exactly in local disk file system paths!), form submit to
```
http://localhost:8080/contextname/servlet 
```
this 1 must work!
the canonical approach, however, make url domain-relative don't need fix urls once again when happen move jsp files around folder.
```
<form action="${pagecontext.request.contextpath}/servlet"> 
```
this generate
```
<form action="/contextname/servlet"> 
```
which submit right url.

use straight quotes in html

you need make absolutely sure you're using straight quotes in html attributes action="..." or action='...' , not curly quotes action=”...” or action=’...’. curly quotes not supported in html , become part of value.

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