新建servlet helloWorld

Question

我是使用servlet的新手。我想运行一个简单的helloWorld servlet代码，但是当运行它时，我得到了这个404错误:请求的资源()不可用。

我的项目名称是"ServletPractice“。

我的java类是：

package one;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorld extends HttpServlet {

private String message;

public void init(){
    message = "hello world";
}

public void doGet(HttpServletRequest request , HttpServletResponse response) throws IOException , ServletException{
    response.setContentType("text/html");

    PrintWriter out = response.getWriter();
    out.println("<h1>" + message + "</h1>");
}

public void destroy()
  {
      // do nothing.
  }

/**
 * @param args
 */
public static void main(String[] args) {
    // TODO Auto-generated method stub

}

}

我的web.xml是：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
<display-name>ServletPractice</display-name>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>
<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.localizationContext</param-name>
<param-value>resources.application</param-value>
</context-param>
<context-param>
<description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>client</param-value>
</context-param>
<context-param>
<description>
This parameter tells MyFaces if javascript code should be allowed in
the rendered HTML output.
If javascript is allowed, command_link anchors will have javascript code
that submits the corresponding form.
If javascript is not allowed, the state saving info and nested parameters
will be added as url parameters.
Default is 'true'</description>
<param-name>org.apache.myfaces.ALLOW_JAVASCRIPT</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<description>
If true, rendered HTML code will be formatted, so that it is 'human-readable'
i.e. additional line separators and whitespace will be written, that do not
influence the HTML code.
Default is 'true'</description>
<param-name>org.apache.myfaces.PRETTY_HTML</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.DETECT_JAVASCRIPT</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<description>
If true, a javascript function will be rendered that is able to restore the
former vertical scroll on every request. Convenient feature if you have pages
with long lists and you do not want the browser page to always jump to the top
if you trigger a link or button action that stays on the same page.
Default is 'false'
</description>
<param-name>org.apache.myfaces.AUTO_SCROLL</param-name>
<param-value>true</param-value>
</context-param>
<listener>
<listener-class>org.apache.myfaces.webapp.StartupServletContextListener</listener-class>
</listener>

<servlet>
<servlet-name>ServletPractice</servlet-name>
<servlet-class>ServletPractice</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ServletPractice</servlet-name>
<url-pattern>/ServletPractice</url-pattern>
</servlet-mapping>

</web-app>

错误：

HTTP Status 404 -

type: Status report

message:

description: The requested resource () is not available.
Apache Tomcat/7.0.16

我在地址栏中的地址是: localhost:9090/ServletPractice/WEB-INF/web.xml

请帮帮我。谢谢

Answer 1

您没有在web.xml中直接映射servlet。您提供的是项目名称而不是Servlet名称，请尝试执行以下操作：

<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>one.HelloWorld</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>

在web.xml中进行更改后，请确保已重新启动服务器

Answer 2

您需要在web.xml文件中添加Servlet声明，如下所示：

<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>one.HelloWorld</servlet-class>
</servlet>

然后将映射添加到此Servlet

<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/HelloWorld</url-pattern> // or the pattern you want
</servlet-mapping>

Answer 3

您需要在web.xml文件中为您的servlet添加servlet声明和url映射。您的yourservletname类名与包

<servlet-mapping>
<servlet-name>yourservletname</servlet-name>
<url-pattern>/yourservletname</url-pattern>

​