• Jsp 学习笔记

    代码可参考: Demo地址

    1 入门

    1.1 环境搭建

    创建moven项目目录结构如下
    在这里插入图片描述

    1.2 依赖配置

    
<dependencies>
    <dependency>
        <groupId>javax.servletgroupId>
        <artifactId>javax.servlet-apiartifactId>
        <version>3.1.0version>
        <scope>providedscope>
    dependency>

    <dependency>
        <groupId>javax.servlet.jspgroupId>
        <artifactId>jsp-apiartifactId>
        <version>2.2version>
        <scope>providedscope>
    dependency>
dependencies>


<plugins>
   <plugin>
       <groupId>org.apache.tomcat.mavengroupId>
       <artifactId>tomcat7-maven-pluginartifactId>
       <version>2.2version>
   plugin>
plugins>

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    1.3 创建页面

    在webapp下创建 hello.jsp

    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Titletitle>
head>
<body>
	<h1>hello jsph1>
    <%
        System.out.println("hello, jso~");
    %>
body>
html>

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    1.4 测试

    启动tomcat
    访问 http://localhost:8080/Jsp-Demo/hello.jsp后
    控制台输出

    hello, jso~

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    2 原理

    hello.jsp是Servlet
    访问hello.jsp会生成如下的类
    在这里插入图片描述
    继承关系

    class HttpJspBase extends HttpServlet implements HttpJspPage

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    public final class hello_jsp extends HttpJspBase implements JspSourceDependent {
    private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();
    private static Map<String, Long> _jspx_dependants;
    private ExpressionFactory _el_expressionfactory;
    private InstanceManager _jsp_instancemanager;

    public hello_jsp() {
    }

    public Map<String, Long> getDependants() {
        return _jspx_dependants;
    }

    public void _jspInit() {
        this._el_expressionfactory = _jspxFactory.getJspApplicationContext(this.getServletConfig().getServletContext()).getExpressionFactory();
        this._jsp_instancemanager = InstanceManagerFactory.getInstanceManager(this.getServletConfig());
    }

    public void _jspDestroy() {
    }

    public void _jspService(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        JspWriter out = null;
        JspWriter _jspx_out = null;
        PageContext _jspx_page_context = null;

        try {
            response.setContentType("text/html;charset=UTF-8");
            PageContext pageContext = _jspxFactory.getPageContext(this, request, response, (String)null, true, 8192, true);
            _jspx_page_context = pageContext;
            pageContext.getServletContext();
            pageContext.getServletConfig();
            pageContext.getSession();
            out = pageContext.getOut();
            out.write("\n");
            out.write("\n");
            out.write("\n");
            out.write("    Title\n");
            out.write("\n");
            out.write("\n");
            out.write("    
    hello jsp
    \n"    );
            out.write("    ");
            System.out.println("hello, jso~");
            out.write("\n");
            out.write("\n");
            out.write("\n");
        } catch (Throwable var13) {
            if (!(var13 instanceof SkipPageException)) {
                out = (JspWriter)_jspx_out;
                if (_jspx_out != null && ((JspWriter)_jspx_out).getBufferSize() != 0) {
                    try {
                        out.clearBuffer();
                    } catch (IOException var12) {
                    }
                }

                if (_jspx_page_context == null) {
                    throw new ServletException(var13);
                }

                _jspx_page_context.handlePageException(var13);
            }
        } finally {
            _jspxFactory.releasePageContext(_jspx_page_context);
        }

    }
}

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    在_jspService()方法中，会将html标签写入到JspWritter中返回给浏览器

    3 jsp实践

    3.1 jsp类型

    3.1.1 <%…%>

    内容会被放到_jspService()中

    3.1.2 <%=…%>

    内容会放到out.println()中，作为out.print()函数

    3.1.3 <%!..%>

    内容会被放到_jspService()方法之外，被类直接包含

    下面是示例

    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Titletitle>
head>
<body>
<h1>hello jsph1>
    <%
        System.out.println("hello, jso~");
        int i = 5;
    %>

    <%="hello"%>
    <%=i%>

    <%!
        void show() {}
        String name = "zhangsan";
    %>
body>
html>

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    public final class hello_jsp extends HttpJspBase implements JspSourceDependent {
	//<%!void show() {} String name = "zhangsan"; %>
    String name = "zhangsan";
    void show() {}
    public void _jspService(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        	...
            System.out.println("hello, jso~"); //<%System.out.println("hello, jso~");%>
            int i = 5; //<% int i = 5%>
            out.write("\n");
            out.write("\n");
            out.write("    ");
            out.print("hello"); //<%="hello"%>
            out.write("\n");
            out.write("    ");
            out.print(i);	// <%=i%>
            ...
        }
    }
}

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    3.2 示例

    <%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ page import="com.jsp.Brand" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%
    List<Brand> brandList = new ArrayList();
    brandList.add(new Brand(1, "华为", "华为", 200, "5G厂商", 1));
    brandList.add(new Brand(2, "比亚迪", "比亚迪", 300, "国产电车", 1));
    brandList.add(new Brand(3, "茅台", "茅台", 400, "白酒酱香", 1));
%>
<html>
<head>
    <title>Titletitle>
head>
<body>
<input type="button" value="新郑"><br>
<hr>
<table border="1" cellspacing="0" width="800">
    <tr>
        <th>序号th>
        <th>品牌名称th>
        <th>企业名称th>
        <th>排序th>
        <th>品牌介绍th>
        <th>状态th>
        <th>操作th>
    tr>

    <%
        for (int i = 0; i < brandList.size(); i++) {
            Brand brand = brandList.get(i);
    %>

    <tr align="center">
        <td><%=brand.getId()%>td>
        <td><%=brand.getBrandName()%>td>
        <td><%=brand.getCompanyName()%>td>
        <td><%=brand.getOrdered()%>td>
        <td><%=brand.getDescription()%>td>
        <td><%=brand.getStatus() == 1 ? "启用" : "禁用"%>td>
        <td><a href="#">修改a> <a href="#">删除a> td>
    tr>

    <%
        }
    %>
table>

body>
html>


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    在浏览器地址栏输入

    http://localhost:8080/Jsp-Demo/brand.jsp

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    效果展示
    在这里插入图片描述

    遇到报错

    Only a type can be imported. * resolves to a package

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    解决方式: 在Avaliable Elements 这里选择对应的项目后，右键，选择 Put into Output Root
    在这里插入图片描述

    4 EL表达式

    EL(全称Expression Language) 表达式语言，用于简化jsp页面的Java代码
    主要作用是获取数据，然后展示在页面上
    语法$ {expression}，如${brands}就是获取域中存储的key为brands的数据

    4.1 案例

    <%@ page contentType="text/html;charset=UTF-8"  isELIgnored="false" language="java" %>
<html>
<head>
    <title>Titletitle>
head>
<body>
    ${brands}
body>
html>

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    @WebServlet("/demo1")
public class ServletDemo1 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("ServletDemo1 doGet");
        List<Brand> brandList = new ArrayList();
        brandList.add(new Brand(1, "华为", "华为", 200, "5G厂商", 1));
        brandList.add(new Brand(2, "比亚迪", "比亚迪", 300, "国产电车", 1));
        brandList.add(new Brand(3, "茅台", "茅台", 400, "白酒酱香", 1));

        req.setAttribute("brands", brandList);
        req.setAttribute("status", 111);

        System.out.println(req.getAttribute("brands"));

        req.getRequestDispatcher("/el-demo.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}


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    访问http://localhost:8080/Jsp-Demo/demo1
    后将会输出brands中的内容

    如果el表达式获取不到值,则可能是WEB-INF包下的web.xml中的版本过低
    修改成

    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://xmlns.jcp.org/xml/ns/javaee"
        xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
        version="3.1">
web-app>

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    另外jsp中添加 isELIgnored=“false”

    <%@ page contentType="text/html;charset=UTF-8"  isELIgnored="false" language="java" %>

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    4.2 域对象

    page: 当前页面有效
    request: 当前请求有效
    session: 当前会话有效
    applicaton: 当前应用有效

    6 JSTL标签

    jsp标准标签库(jsp Standarded Tab Library), 使用标签替代jsp页面上的代码
    使用:
    导入依赖

    <dependency>
   <groupId>jstlgroupId>
   <artifactId>jstlartifactId>
   <version>1.2version>
dependency>
<dependency>
    <groupId>taglibsgroupId>
    <artifactId>standardartifactId>
    <version>1.1.2version>
dependency>

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    使用标签

    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

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    使用示例:
    jstp.jsp

    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<html>
<head>
    <title>Titletitle>
head>
<body>
    <%-- <c:if>标签 --%>
    <c:if test="${status == 1}">
        开启
    c:if>

    <c:if test="${status == 0}">
        关闭
    c:if>
    <br>

    <%-- <c:forEach>标签 --%>
    <c:forEach items="${brands}" var="brand">
        <tr align="center">
            <td>${brand.id}td>
            <td>${brand.brandName}td>
            <td>${brand.companyName}td>
            <td>${brand.description}td>
        tr>
        <br>
    c:forEach>
    <br>

    <%-- <c:forEach>标签 --%>
    <c:forEach begin="0" end="10" step="1" var="i">
        ${i}
    c:forEach>

body>
html>

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    ServletDemo2.java

    @WebServlet("/demo2")
public class ServletDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //将数据存储到request域中
        req.setAttribute("status", 1);

        List<Brand> brandList = new ArrayList<>();
        brandList.add(new Brand(1, "华为", "华为", 200, "5G厂商", 1));
        brandList.add(new Brand(2, "比亚迪", "比亚迪", 300, "国产电车", 1));
        brandList.add(new Brand(3, "茅台", "茅台", 400, "白酒酱香", 1));

        req.setAttribute("brands", brandList);

        //转发到jstl-if.jsp中
        req.getRequestDispatcher("/jstl.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

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    使用浏览器访问

    http://localhost:8080/Jsp-Demo/demo2

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    浏览器中输出内容

    开启
1 华为 华为 5G厂商
2 比亚迪 比亚迪 国产电车
3 茅台 茅台 白酒酱香

0 1 2 3 4 5 6 7 8 9 10

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    7 示例

    7.1 环境准备

    1 创建web工程
    2 创建数据库，添加数据

    -- 创建tb_brand表
create table tb_brand(
	id int primary key auto_increment,
	brand_name varchar(20),
	company_name varchar(20),
	ordered int,
	description varchar(100),
	status int
);

-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values('比亚迪', '比亚迪汽车有限公司', 100, '高科技专业电动汽车', 0),
	  ('宁德时代', '宁德时代科技公司', 200, '高科技锂电池', 1),
	  ('小米', '小米科技有限公司', 300, '让每个人享受科技带来的美好生活', 1)

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    7.2 查询所有

    1 配置web-app的版本，否则jsp中获取不到el表达式的值
    WEB-INFO/web.xml

    DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
web-app>

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    2 实体类 Brand

    package com.test.pojo;

public class Brand {
    private Integer id;
    private String brandName;
    private String companyName;
    private Integer ordered;
    private String description;
    private Integer status;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Brand{" +
                "id=" + id +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}


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    3 定义公共的查询工具类

    package com.test.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String rescource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(rescource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }
}

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    4 定义查询的Mapper类和xml
    BrandMapper.java

    public interface BrandMapper {
    List<Brand> selectAll();
}

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    BrandMapper.xml

    
DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.test.mapper.BrandMapper">
    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName">result>
        <result column="company_name" property="companyName">result>
    resultMap>

    <select id="selectAll" resultType="com.test.pojo.Brand" resultMap="brandResultMap">
        select * from tb_brand;
    select>
mapper>

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    5 定义查询的方法

    public class BrandService {
    SqlSessionFactory factory  = SqlSessionFactoryUtils.getSqlSessionFactory();

    public List<Brand> selectAll() {
        SqlSession sqlSession = factory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        List<Brand> brands = mapper.selectAll();
        System.out.println("brands = " + brands);
        sqlSession.close();
        return brands;
    }
}

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    6 定义服务接口Servlet

    @WebServlet("/selectAllServlet")
public class SelectAllServlet extends HttpServlet {
    private BrandService service = new BrandService();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<Brand> brands = service.selectAll();
        req.setAttribute("brands", brands);
        req.getRequestDispatcher("/brand.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

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    7 jsp页面

    <%--
  Created by IntelliJ IDEA.
  User: yl
  Date: 2022/11/30
  Time: 5:11 PM
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Titletitle>
head>
<body>
  <hr>
  <table border="1" cellspacing="0" width="80%">
    <tr>
        <th>序号th>
        <th>品牌名称th>
        <th>企业名称th>
        <th>排序th>
        <th>品牌介绍th>
        <th>状态th>
        <th>操作th>
    tr>
      <c:forEach items="${brands}" var="brand" varStatus="status">
          <tr align="center">
              <td>${status.count}td>
              <td>${brand.brandName}td>
              <td>${brand.companyName}td>
              <td>${brand.ordered}td>
              <td>${brand.description}td>
              <c:if test="${brand.status == 1}">
                  <td>启用td>
              c:if>

               <c:if test="${brand.status != 1}">
                  <td>禁用td>
              c:if>
              <td>
                  <a href="/Mvc-Demo/selectByIdServlet?id=${brand.id}">修改

                  a> <a href="#"> 删除a>
              td>
          tr>
      c:forEach>
  table>
body>
html>

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    访问http://localhost:8080/Mvc-Demo/selectAllServlet地址后，
    浏览器页面效果
    在这里插入图片描述

    7.3 添加

    具体代码可参考顶部Demo中
    1 Mapper方法

    @Insert("insert into tb_brand values(null, #{brandName}, #{companyName}," +
        " #{ordered}, #{description}, #{status})")
void add(Brand brand);

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    2 Service中的方法

    public void add(Brand brand) {
   SqlSession sqlSession = factory.openSession();
    BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

    mapper.add(brand);
    sqlSession.commit();
    sqlSession.close();
}

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    3 添加页面jsp

    <%--
  Created by IntelliJ IDEA.
  User: yl
  Date: 2022/11/30
  Time: 9:16 PM
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>添加品牌title>
head>
<body>
    <h3>添加品牌h3>
    <form action="/Mvc-Demo/addServlet" method="post">
        品牌名称: <input name="brandName"><br> <br>
        企业名称: <input name="companyName"><br> <br>
        品牌排序: <input name="ordered"><br> <br>
        描述信息: <textarea rows="5" cols="20" name="description">textarea> <br> <br>
        状态:
        <input type="radio" name="status" value="0">禁用
        <input type="radio" name="status" value="1">启用 <br><br>

        <input type="submit" value="提交">
    form>
body>
html>

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    4 Servlet接口

    package com.test.web;

import com.test.pojo.Brand;
import com.test.service.BrandService;

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;
import java.util.List;

@WebServlet("/selectAllServlet")
public class SelectAllServlet extends HttpServlet {
    private BrandService service = new BrandService();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<Brand> brands = service.selectAll();
        req.setAttribute("brands", brands);
        req.getRequestDispatcher("/brand.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

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    5 列表页面新增

    <input type="button" value="新增" id="add"><br>

<script>
    document.getElementById("add").onclick = function () {
        location.href = "/Mvc-Demo/addBrand.jsp"
    }
script>

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    请求地址: http://localhost:8080/Mvc-Demo/addBrand.jsp
    效果展示
    在这里插入图片描述
    提交后，商品列表中多了一项
    在这里插入图片描述

    7.4 查询并展示单条数据

    1 BrandMapper中添加查询语句

    @Select("select * from tb_brand where id = #{id}")
@ResultMap("brandResultMap")
Brand selectById(int id);

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    2 BrandService添加查询Mapper逻辑

    public Brand selectById(int id) {
    SqlSession sqlSession = factory.openSession();
    BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

    Brand brand = mapper.selectById(id);
    sqlSession.commit();
    sqlSession.close();

    return brand;
}

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    3 添加查询的Servlet

    @WebServlet("/selectByIdServlet")
public class SelectByIdServlet extends HttpServlet {
    private BrandService service = new BrandService();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String id = req.getParameter("id");
        Brand brand = service.selectById(Integer.parseInt(id));
        req.setAttribute("brand", brand);

        req.getRequestDispatcher("/update.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

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    4 添加update.jsp

    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<html>
<head>
    <title>修改品牌信息title>
head>
<body>
    <h3>修改品牌信息h3>
    <form action="/Mvc-Demo/updateServlet" method="post">
        品牌名称: <input name="brandName" value="${brand.brandName}"><br> <br>
        企业名称: <input name="companyName" value="${brand.companyName}"><br> <br>
        品牌排序: <input name="ordered" value="${brand.ordered}"><br> <br>
        描述信息: <textarea rows="5" cols="20" name="description"> ${brand.description} textarea> <br> <br>
        状态:
        <c:if test="${brand.status == 0}">
            <input type="radio" name="status" value="0" checked>禁用
            <input type="radio" name="status" value="1">启用 <br><br>
        c:if>

        <c:if test="${brand.status == 1}">
            <input type="radio" name="status" value="0">禁用
            <input type="radio" name="status" value="1" checked>启用 <br><br>
        c:if>


        <input type="submit" value="提交">
    form>
body>
html>

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    5 访问http://localhost:8080/Mvc-Demo/selectAllServlet 后，选择任意一项品牌，然后点修改
    展示效果:
    在这里插入图片描述

    7.5 修改

    1 添加update sql 语句方法
    BrandMapper.java

    @Update("update tb_brand set brand_name = #{brandName}, company_name = #{companyName}, ordered = #{ordered}" +
        ", description = #{description}, status = #{status} where id = #{id}")
void update(Brand brand);

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    2 添加业务方法

    public void update(Brand brand) {
    SqlSession sqlSession = factory.openSession();
    BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

    System.out.println("update brand = " + brand);
    mapper.update(brand);
    sqlSession.commit();
    sqlSession.close();
}

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    3 updateServlet

    WebServlet("/updateServlet")
public class UpdateServlet extends HttpServlet {
	private BrandService service = new BrandService();
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
	   req.setCharacterEncoding("utf-8");
	
	   String id = req.getParameter("id");
	   String brandName = req.getParameter("brandName");
	   String companyName = req.getParameter("companyName");
	   String ordered = req.getParameter("ordered");
	   String description = req.getParameter("description");
	   String status = req.getParameter("status");
	
	   Brand brand = new Brand();
	   brand.setBrandName(brandName);
	   brand.setCompanyName(companyName);
	   brand.setOrdered(Integer.parseInt(ordered));
	   brand.setDescription(description);
	   brand.setStatus(Integer.parseInt(status));
	   brand.setId(Integer.parseInt(id));
	
	   service.update(brand);
	
	   req.getRequestDispatcher("/selectAllServlet").forward(req, resp);
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
	    this.doGet(req, resp);
	}
}

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    4 隐藏id选项，id不可编辑

    <input type="hidden" name="id" value="${brand.id}"><br>

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    在update.jsp页面中，修改内容，提交后，可看到内容被修改了

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  • 原文地址：https://blog.csdn.net/SImple_a/article/details/128055200