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java servlet

admin 11月 12, 2020 0

Servlet提供了一种基于组件的跨平台的搭建Web应用的方法，而且没有CGI程序的性能限制。

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <artifactId>hello-servlet</artifactId>
  <groupId>io.github.bryceliu</groupId>
  <version>1.0.0</version>
  <packaging>war</packaging>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>
  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
    </dependency>
  </dependencies>
  <build>
    <sourceDirectory>src/main/java</sourceDirectory>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.3</version>
        <configuration>
          <warSourceDirectory>src/main/webapp</warSourceDirectory>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.1</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<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_3_1.xsd"
  version="3.1"
  metadata-complete="true">
  <filter>
      <filter-name>UserFilter</filter-name>
      <filter-class>io.github.bryceliu.filter.UserFilter</filter-class>
      <init-param>
          <param-name>init-name</param-name>
          <param-value>NAME</param-value>
      </init-param>
  </filter>
  <filter>
      <filter-name>AuthFilter</filter-name>
      <filter-class>io.github.bryceliu.filter.AuthFilter</filter-class>
      <init-param>
          <param-name>init-role</param-name>
          <param-value>ROLE</param-value>
      </init-param>
  </filter>
  <filter-mapping>
      <filter-name>UserFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  <filter-mapping>
      <filter-name>AuthFilter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  <servlet>
      <servlet-name>UserServlet</servlet-name>
      <servlet-class>io.github.bryceliu.servlet.UserServlet</servlet-class>
  </servlet>
  <servlet>
      <servlet-name>ErrorHandler</servlet-name>
      <servlet-class>io.github.bryceliu.servlet.ErrorHandler</servlet-class>
  </servlet>
  <servlet>
      <servlet-name>NotFound</servlet-name>
      <servlet-class>io.github.bryceliu.servlet.NotFound</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>UserServlet</servlet-name>
      <url-pattern>/user</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
      <servlet-name>ErrorHandler</servlet-name>
      <url-pattern>/error</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
      <servlet-name>NotFound</servlet-name>
      <url-pattern>/notfound</url-pattern>
  </servlet-mapping>
  <error-page>
      <exception-type>java.lang.RuntimeException</exception-type>
      <location>/error</location>
  </error-page>
  <error-page>
      <error-code>404</error-code>
      <location>/notfound</location>
  </error-page>
</web-app>

UserServlet.java

package io.github.bryceliu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Objects;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class UserServlet extends HttpServlet {
    private static final long serialVersionUID = 7396591690444306320L;
    
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet");
        PrintWriter writer = resp.getWriter();
        String userId = req.getParameter("id");
        if (Objects.equals(userId, "99")) {
            throw new RuntimeException("Forbidden");
        } else if (Objects.equals(userId, "999")) {
            resp.setStatus(404);
        } else {
            resp.setContentType("text/html");
            writer.println("Hello World");
            writer.println(req.getRemoteAddr());
            writer.println(req.getRemoteHost());
        }
    }
}

AuthFilter.java

package io.github.bryceliu.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class AuthFilter implements Filter {
    
    public void init(FilterConfig filterConfig) throws ServletException {
        
        System.out.println("Auth Filter init " + filterConfig.getInitParameter("init-name"));
    }
    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        
        System.out.println("---------------------------------------------");
        System.out.println(request.getRemoteAddr() + " Auth " + System.currentTimeMillis());
        chain.doFilter(request, response);
    }
    
    public void destroy() {
        
        System.out.println("Auth Filter destroy");
    }
}