• servlet介绍

    servlet技术用于处理页面的请求，创建servletJAVA类，里面有响应页面请求的方法

    servlet的生命周期为：

    1. package Servlet;
    2.  
    3. import java.io.IOException;
    4. import jakarta.servlet.ServletConfig;
    5. import jakarta.servlet.ServletException;
    6. import jakarta.servlet.annotation.WebServlet;
    7. import jakarta.servlet.http.HttpServlet;
    8. import jakarta.servlet.http.HttpServletRequest;
    9. import jakarta.servlet.http.HttpServletResponse;
    10.  
    11. /**
    12.  * Servlet implementation class Servletshengmingzhouqi
    13.  */
    14. //@WebServlet("/Servletshengmingzhouqi")
    15. public class Servletshengmingzhouqi extends HttpServlet {
    16. 	private static final long serialVersionUID = 1L;
    17.  
    18. 	/**
    19. 	 * Default constructor.
    20. 	 */
    21. 	static {
    22. 		System.out.println("Servlet被加载....");
    23. 	}
    24.  
    25. 	public Servletshengmingzhouqi() {
    26. 		System.out.println("Servlet被实例化....");
    27. 	}
    28.  
    29. 	/**
    30. 	 * @see Servlet#init(ServletConfig)
    31. 	 */
    32. 	public void init(ServletConfig config) throws ServletException {
    33. 		System.out.println("Servlet被初始化....");
    34. 	}
    35.  
    36. 	/**
    37. 	 * @see Servlet#destroy()
    38. 	 */
    39. 	public void destroy() {
    40. 		System.out.println("Servlet被销毁....");
    41. 	}
    42.  
    43. 	/**
    44. 	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
    45. 	 *      response)
    46. 	 */
    47. 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    48. 			throws ServletException, IOException {
    49. 		System.out.println("Servlet请求处理中....");
    50. 	}
    51.  
    52. 	/**
    53. 	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
    54. 	 *      response)
    55. 	 */
    56. 	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    57. 			throws ServletException, IOException {
    58. 		System.out.println("Servlet请求服务中....");
    59. 	}
    60.  
    61. }

    加载-实例化-初始化-处理-销毁

     

      servlet类中的主要方法就是：

    init：初始化方法，在构造函数后面调用

    destroy：销毁方法，在手动关闭servlet时调用

    doGet、doPost：浏览器使用get、post方法时调用指定方法

    默认情况下，浏览器发送请求时servlet进行加载-实例化-初始化，不过可以在wep.xml配置默认服务器开启时自动 加载-实例化-初始化：

    1

    给定的数字参数越大，服务器在实例化它时优先级就越高，0为浏览器发送请求时实例化

     浏览器页面若想使用servlet就需要配置路径：

    1. 	<servlet>
    2. 		<servlet-name>smzqservlet-name>
    3. 		<servlet-class>Servlet.Servletshengmingzhouqiservlet-class>
    4. 	
    5. 	servlet>
    6. 	<servlet-mapping>
    7. 		<servlet-name>smzqservlet-name>
    8. 		<url-pattern>/Servletsmzqurl-pattern>
    9. 	servlet-mapping>

    servlet-name：servlet的别名

    servlet-class：servlet类的地址

    url-pattern：将servlet访问地址切换为这个名字，form地址栏可以直接用这个地址

     以上配置文件也许有一些繁琐，也可以直接在servlet类中配置：

    @WebServlet("/Servletsmzq")

     这两种方法选其中一种就像，但是同时只能出现一种，不然你懂的：

    既然已经了解了基本方法，我们来写一个网页提交信息的练习：

    写前端：

    1. <%@ page language="java" contentType="text/html; charset=UTF-8"
    2. 	pageEncoding="UTF-8"%>
    3. html>
    4. <html>
    5. <head>
    6. <meta charset="UTF-8">
    7. <title>Insert title heretitle>
    8. head>
    9. <body>
    10. 	<form action="AddServlet" method="post">
    11. 		<table border="1px">
    12. 			<tr>
    13. 				<td>商品名称td>
    14. 				<td><input type="text" name="name" />td>
    15. 			tr>
    16. 			<tr>
    17. 				<td>商品编号td>
    18. 				<td><input type="text" name="on" />是否递增<input type="checkbox"
    19. 					name="diZeng" value="auto" />td>
    20.  
    21. 			tr>
    22. 			<tr>
    23. 				<td>商品品牌td>
    24. 				<td><input type="text" name="logo" />td>
    25. 			tr>
    26. 			<tr>
    27. 				<td>供应商td>
    28. 				<td><input type="text" name="supplier" />td>
    29. 			tr>
    30. 			<tr>
    31. 				<td>商品价格td>
    32. 				<td><input type="text" name="price" />td>
    33. 			tr>
    34. 			<tr>
    35. 				<td>商品备注td>
    36. 				<td><input type="text" name="remark" />td>
    37. 			tr>
    38. 			<tr>
    39. 				<td colspan="2" align="center" id="cuoWu">
    40. 					<%
    41. 					Object s = request.getAttribute("error");
    42. 					if (s != null) {
    43. 					%> <span style="color: red"> <%=s%>
    44. 				span> <%
    45.  }
    46.  %>
    47. 				td>
    48. 			tr>
    49. 			<tr>
    50. 				<td colspan="2" align="center"><input type="submit" value="添加"
    51. 					onclick="cheak()" /><input type="button" value="返回"
    52. 					onclick="history.back()" />td>
    53. 			tr>
    54. 		table>
    55. 	form>
    56. body>
    57. html>

    写pojo：

    1. package Pojo;
    2.  
    3. import java.util.ArrayList;
    4. import java.util.List;
    5.  
    6. public class ShangPin {
    7. 	public static List ShangPinList = new ArrayList<>();
    8. 	public static int baseNo = 0;
    9. 	private String name;// 名字
    10. 	private int on;// 编号
    11. 	private String logo;// 品牌
    12. 	private String supplier;// 供应商
    13. 	private double price;// 价格
    14. 	private String remark;// 备注
    15.  
    16. 	public ShangPin(String name, int on, String logo, String supplier, double price, String remark) {
    17. 		this.name = name;
    18. 		this.on = on;
    19. 		this.logo = logo;
    20. 		this.supplier = supplier;
    21. 		this.price = price;
    22. 		this.remark = remark;
    23. 	}
    24.  
    25. 	public String getName() {
    26. 		return name;
    27. 	}
    28.  
    29. 	public void setName(String name) {
    30. 		this.name = name;
    31. 	}
    32.  
    33. 	public int getOn() {
    34. 		return on;
    35. 	}
    36.  
    37. 	public void setOn(int no) {
    38. 		this.on = no;
    39. 	}
    40.  
    41. 	public String getLogo() {
    42. 		return logo;
    43. 	}
    44.  
    45. 	public void setLogo(String logo) {
    46. 		this.logo = logo;
    47. 	}
    48.  
    49. 	public String getSupplier() {
    50. 		return supplier;
    51. 	}
    52.  
    53. 	public void setSupplier(String supplier) {
    54. 		this.supplier = supplier;
    55. 	}
    56.  
    57. 	public double getPrice() {
    58. 		return price;
    59. 	}
    60.  
    61. 	public void setPrice(double price) {
    62. 		this.price = price;
    63. 	}
    64.  
    65. 	public String getRemark() {
    66. 		return remark;
    67. 	}
    68.  
    69. 	public void setRemark(String remark) {
    70. 		this.remark = remark;
    71. 	}
    72. }

    写Servlet：

    1. package Servlet;
    2.  
    3. import java.io.IOException;
    4.  
    5. import Pojo.ShangPin;
    6. import jakarta.servlet.ServletException;
    7. import jakarta.servlet.annotation.WebServlet;
    8. import jakarta.servlet.http.HttpServlet;
    9. import jakarta.servlet.http.HttpServletRequest;
    10. import jakarta.servlet.http.HttpServletResponse;
    11.  
    12. /**
    13.  * Servlet implementation class AddServlet
    14.  */
    15. @WebServlet("/AddServlet")
    16. public class AddServlet extends HttpServlet {
    17. 	private static final long serialVersionUID = 1L;
    18.  
    19. 	/**
    20. 	 * Default constructor.
    21. 	 */
    22. 	public AddServlet() {
    23. 		// TODO Auto-generated constructor stub
    24. 	}
    25.  
    26. 	/**
    27. 	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
    28. 	 *      response)
    29. 	 */
    30. 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    31. 			throws ServletException, IOException {
    32. 		doPost(request, response);
    33. 	}
    34.  
    35. 	/**
    36. 	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
    37. 	 *      response)
    38. 	 */
    39. 	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    40. 			throws ServletException, IOException {
    41. 		request.setCharacterEncoding("utf-8");
    42. 		String name = request.getParameter("name");// 名字
    43. 		String logo = request.getParameter("logo");// 获取品牌
    44. 		String supplier = request.getParameter("supplier");// 供应商
    45. 		String price = request.getParameter("price");// 价格
    46. 		String remark = request.getParameter("remark");// 备注
    47. 		String[] cbx = request.getParameterValues("diZeng");// 递增
    48. 		String on = "";
    49. 		if (cbx != null) {
    50. 			on = "" + (++(ShangPin.baseNo));
    51. 		} else {
    52. 			on = request.getParameter("on");// 编号
    53. 		}
    54. 		if (name.equals("") || logo.equals("") || supplier.equals("") || price.equals("") || remark.equals("")
    55. 				|| on.equals("")) {
    56. 			request.setAttribute("error", "数据不能少");
    57. 			request.getRequestDispatcher("ZhuYe.jsp").forward(request, response);
    58. 		} else {
    59. 			ShangPin sp = new ShangPin(name, Integer.parseInt(on), logo, supplier, Double.parseDouble(price), remark);
    60. 			System.out.println(sp.getName());
    61. 			System.out.println(sp.getOn());
    62. 			System.out.println(sp.getLogo());
    63. 			System.out.println(sp.getSupplier());
    64. 			System.out.println(sp.getPrice());
    65. 			System.out.println(sp.getRemark());
    66. 		}
    67.  
    68. 	}
    69.  
    70. }

    前端负责收集信息、

    提交到后端时，右AddServlet处理信息，把每个数据取出来：

    request.getParameter("")

    request主要用于取出前端提交的信息

    是否递增选项为多选框，使用：

    String[] arr = request.getParameterValues("");

    后端逻辑：

    主要难点为多选框选中时和未选中时；

    选中时不取手动填写编号框

    未选中时取出手动填写编号框

     将所有数据取出后同一进行非空判断，

    如果不满足利用重定义方法重新定义到前端页面

    request.setAttribute("error", "数据不能少");//定义传回前端的提示数据
    request.getRequestDispatcher("ZhuYe.jsp").forward(request, response);//定义重定义页面，和传回的数据

    逻辑比较简单，仔细一点就能完成，404、500不要怕，奥里给！！干就完了！！ 

    Servlet返回响应response使用

    1. response.setContentType("text/html;charset=UTF-8");
    2. 			PrintWriter out = response.getWriter();
    3. 			out.println("
      " + sp.getName() + "
      "      );
    4. 			out.println("
      " + sp.getOn() + "
      "      );
    5. 			out.println("
      " + sp.getLogo() + "
      "      );
    6. 			out.println("
      " + sp.getSupplier() + "
      "      );
    7. 			out.println("
      " + sp.getPrice() + "
      "      );
    8. 			out.println("
      " + sp.getRemark() + "
      "      );

    首先设置编码格式，获取输出对象、输出 

    显示当前登录名和安全退出按钮：

    使用session存入数据，只要浏览器没被关闭，就能使用

    登录页面：

    1. <%@ page language="java" contentType="text/html; charset=UTF-8"
    2. 	pageEncoding="UTF-8"%>
    3. html>
    4. <html>
    5. 	<head>
    6. 		<meta charset="UTF-8">
    7. 		<title>Insert title heretitle>
    8. 	head>
    9. 	<body>
    10. 		<form action="loginServlet" method="post">
    11. 			<table border="1px">
    12. 				<tr>
    13. 					<td>
    14. 						用户名:
    15. 					td>
    16. 					<td>
    17. 						<input type="text" name=name />
    18. 					td>
    19. 				tr>
    20. 				<tr>
    21. 					<td>密码:td>
    22. 					<td><input type="password" name="pwd" />td>
    23. 				tr>
    24. 				<tr>
    25. 					<td>
    26. 						<%Object s=request.getAttribute("error");
    27. 						if(s!=null){
    28. 							out.print("<p style='color:red'>"+s+"p>");
    29. 						}
    30. 						%>
    31. 					
    32. 					td>
    33. 					<td><input type="submit" value="登录" />td>
    34. 				tr>
    35. 			table>
    36. 			
    37. 			
    38. 		form>
    39. 	body>
    40. html>

    处理登录servlet类：

    1. package Servlet;
    2.  
    3. import java.io.IOException;
    4. import jakarta.servlet.ServletException;
    5. import jakarta.servlet.annotation.WebServlet;
    6. import jakarta.servlet.http.HttpServlet;
    7. import jakarta.servlet.http.HttpServletRequest;
    8. import jakarta.servlet.http.HttpServletResponse;
    9. import jakarta.servlet.http.HttpSession;
    10.  
    11. /**
    12.  * Servlet implementation class loginServlet
    13.  */
    14. @WebServlet("/loginServlet")
    15. public class loginServlet extends HttpServlet {
    16. 	private static final long serialVersionUID = 1L;
    17.  
    18. 	/**
    19. 	 * Default constructor.
    20. 	 */
    21. 	public loginServlet() {
    22. 		// TODO Auto-generated constructor stub
    23. 	}
    24.  
    25. 	/**
    26. 	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
    27. 	 *      response)
    28. 	 */
    29. 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    30. 			throws ServletException, IOException {
    31. 		doPost(request, response);
    32. 	}
    33.  
    34. 	/**
    35. 	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
    36. 	 *      response)
    37. 	 */
    38. 	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    39. 			throws ServletException, IOException {
    40. 		String name = "test";
    41. 		String pwd = "test";
    42. 		String htmlName = request.getParameter("name");
    43. 		String htmlPwd = request.getParameter("pwd");
    44. 		if (name.equals(htmlName) && pwd.equals(htmlPwd)) {
    45. 			HttpSession session=request.getSession();
    46. 			session.setAttribute("NAME", name);
    47. 			request.getRequestDispatcher("ZhuYe.jsp").forward(request, response);
    48. 		} else {
    49. 			request.setAttribute("error", "用户名或密码错误");
    50. 			request.getRequestDispatcher("login.jsp").forward(request, response);
    51. 		}
    52. 	}
    53.  
    54. }

    显示当前登录名字和安全退出按钮：

    1. <div id="yonghu">
    2. 		<%
    3. 		out.print(session.getAttribute("NAME"));
    4. 		%>
    5. 		<a href="tuiChuServlet">退出登录a>
    6. 	div>

    安全退出servlet类：

    1. package Servlet;
    2.  
    3. import java.io.IOException;
    4. import jakarta.servlet.ServletException;
    5. import jakarta.servlet.annotation.WebServlet;
    6. import jakarta.servlet.http.HttpServlet;
    7. import jakarta.servlet.http.HttpServletRequest;
    8. import jakarta.servlet.http.HttpServletResponse;
    9. import jakarta.servlet.http.HttpSession;
    10. import jakarta.websocket.Session;
    11.  
    12. /**
    13.  * Servlet implementation class tuiChuServlet
    14.  */
    15. @WebServlet("/tuiChuServlet")
    16. public class tuiChuServlet extends HttpServlet {
    17. 	private static final long serialVersionUID = 1L;
    18.  
    19. 	/**
    20. 	 * Default constructor.
    21. 	 */
    22. 	public tuiChuServlet() {
    23. 		// TODO Auto-generated constructor stub
    24. 	}
    25.  
    26. 	/**
    27. 	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
    28. 	 *      response)
    29. 	 */
    30. 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    31. 			throws ServletException, IOException {
    32. 		doPost(request, response);
    33. 	}
    34.  
    35. 	/**
    36. 	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
    37. 	 *      response)
    38. 	 */
    39. 	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    40. 			throws ServletException, IOException {
    41. 		HttpSession session = request.getSession();
    42. 		session.invalidate();
    43. 		request.getRequestDispatcher("login.jsp").forward(request, response);
    44. 	}
    45.  
    46. }

    逻辑为：清除session数据，

    重定义页面。

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  • 原文地址：https://blog.csdn.net/qx020814/article/details/126171134