本专辑将介绍servlet的使用。
我们首先看一下servlet实现的三种基本方式。
1、环境约束
- idea2018.1.5
- maven-3.0.5
- jdk-8u162-windows-x64
- servlet3.0
2、前提约束
3、操作步骤
- 1 加入servlet依赖
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jsp-api</artifactId>
<version>2.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
</dependency>
</dependencies>
- 2 加入tomcat插件
<build>
<finalName>servlet-test</finalName>
<plugins>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<configuration>
<path>/</path>
<port>8088</port>
</configuration>
</plugin>
</plugins>
</build>
- 3 实现servlet
3.1 实现Servlet接口
在src/main/java文件夹下创建net.wanho.servlet包，在该包下创建ServletOne.java文件，内容如下：
package net.wanho.servlet;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/servletone")
public class ServletOne implements Servlet {
@Override
public void init(ServletConfig config) throws ServletException {
}
@Override
public ServletConfig getServletConfig() {
return null;
}
@Override
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
System.out.println("获取页面传递过来的参数，调用下层逻辑，返回响应");
String name = req.getParameter("name");
res.getWriter().write("这是后台返回的数据："+name);
}
@Override
public String getServletInfo() {
return null;
}
@Override
public void destroy() {
}
}
3.2 继承HttpServlet类
在src/main/java文件夹下的net.wanho.servlet包中创建ServletTwo.java文件，内容如下：
package net.wanho.servlet;
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 java.io.IOException;
@WebServlet("/servlettwo")
public class ServletTwo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("获取页面传递过来的参数，调用下层逻辑，返回响应");
String name = req.getParameter("name");
resp.getWriter().write("这是ServletTwo返回的数据："+name);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
3.3 继承GenericServlet类
在src/main/java文件夹下的net.wanho.servlet包中创建ServletTwo.java文件，内容如下：
package net.wanho.servlet;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;
@WebServlet("/servletthree")
public class ServletThree extends GenericServlet {
@Override
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
System.out.println("获取页面传递过来的参数，调用下层逻辑，返回响应");
String name = req.getParameter("name");
res.getWriter().write("这是ServletThree返回的数据："+name);
}
}
- 测试
（1）以maven自带tomcat插件方式启动项目
（2）打开浏览器，分别输入：
http://localhost:8088/servletone?name=ali
http://localhost:8088/servlettwo?name=ali
http://localhost:8088/servletthree?name=ali
则看到三个servlet返回的不同结果。 - 注意：
@WebServlet("/servletone")可以被web.xml中的以下内容代替：
<servlet>
<servlet-name>one</servlet-name>
<servlet-class>net.wanho.servlet.ServletOne</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>one</servlet-name>
<url-pattern>/servletone</url-pattern>
</servlet-mapping>
@WebServlet("/servlettwo")可以被web.xml中的以下内容代替：
<servlet>
<servlet-name>two</servlet-name>
<servlet-class>net.wanho.servlet.ServletTwo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>two</servlet-name>
<url-pattern>/servlettwo</url-pattern>
</servlet-mapping>
@WebServlet("/servletthree")可以被web.xml中的以下内容代替：
<servlet>
<servlet-name>three</servlet-name>
<servlet-class>net.wanho.servlet.ServletThree</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>three</servlet-name>
<url-pattern>/servletthree</url-pattern>
</servlet-mapping>
前者是注解，后者是配置，是实现一件事情的两种不同方式。
