JavaWeb 入门:Hello Servlet

创建JavaWeb项目
打开Eclipse
点击菜单栏“File”->“New”->“Dynamic Web Project”
输入项目名称，然后点击“Next”按钮
选择“Generate web.xml deployment descriptor”，然后点击“Finish”按钮
添加Servlet
在“Package Explorer”视图中右键点击项目名称，选择“New”->“Servlet”
添加Servlet的类名和包名，然后点击“Next”按钮
选择要继承的父类，然后点击“Finish”按钮
配置Servlet
在Servlet类中重写doGet()和doPost()方法
在web.xml中添加Servlet类的映射

示例一：Hello World

@WebServlet(name = "HelloServlet", urlPatterns = "/hello")
public class HelloServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        writer.println("<html>");
        writer.println("<head><title>Hello Servlet</title></head>");
        writer.println("<body>");
        writer.println("<h1>Hello World!</h1>");
        writer.println("</body>");
        writer.println("</html>");
        writer.close();
    }

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

}

在浏览器中输入"http://localhost:8080/<项目名>/hello"，即可看到"Hello World!"字样的显示页面。

示例二：计算器

@WebServlet(name = "CalServlet", urlPatterns = "/cal")
public class CalServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        writer.println("<html>");
        writer.println("<head><title>Calculator</title></head>");
        writer.println("<body>");
        int num1=Integer.parseInt(request.getParameter("num1"));
        int num2=Integer.parseInt(request.getParameter("num2"));
        int res=0;
        String op=request.getParameter("op");
        switch(op){
            case "+":res=num1+num2;break;
            case "-":res=num1-num2;break;
            case "*":res=num1*num2;break;
            case "/":res=num1/num2;break;
        }
        writer.println("<h1>"+num1+op+num2+"="+res+"</h1>");
        writer.println("</body>");
        writer.println("</html>");
        writer.close();
    }

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

}

在浏览器中输入"http://localhost:8080/<项目名>/cal?num1=2&num2=3&op=+"，即可看到"2+3=5"字样的显示页面。

以上就是JavaWeb入门教程的完整攻略及示例说明。

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