运用tomcat在浏览器中对数据库信息进行查询

在idea中创建好项目后，添加web项目

然后打开idea的setting，跳转到下面的页面，下载maven插件。

出现下面的选项，才正确。

添加好web项目后，打开pom文件，添加相应的依赖：

<?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>

    <groupId>org.example</groupId>
    <artifactId>MVCCase</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
<!--        下面俩个依赖是写servlet的-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope><!--provided在编译和测试环境有效  -->
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
            <scope>provided</scope>
        </dependency>

<!--        下面俩个依赖是连接数据库时用到的-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.21</version>
        </dependency>

<!--        下面俩个依赖是工具依赖，在写jsp时会用到-->
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <port>8080</port>
                    <path>/</path>
                </configuration>

            </plugin>
        </plugins>
    </build>
</project>

千万别忘了，写上<packaging>war</packaging> 把打包方式改成打war包。

下面图片是要进行操作的数据库信息:

因为操作数据库过程中用到了mybatis，所以需要配置相应的xml文件，详细的配置过程在前面的Mybatis简化JDBC开发文章中写过。下面这是brandMapper.xml的内容。

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--<mapper namespace="test">-->
<mapper namespace="org.example.Mapper.brandMapper">

    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>
</mapper>

然后创建对应的实体类pojo，接口方法类Mapper和方法实现类service。

pojo实体类：

package org.example.pojo;

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

    public brand(Integer id, String brandName, String companyName, Integer ordered, String description, Integer status) {
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.ordered = ordered;
        this.description = description;
        this.status = status;
    }

    public brand() {
    }

    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;
    }

}

接口方法类Mapper

先写一个查询所有的方法，因为此处需要实现的功能比较简单，所以用注解就行了。

public interface brandMapper {
    //查询全部
    @Select("select * from db.brand")
    @ResultMap("brandResultMap")
    List<brand>selectAll();
}

方法实现类service

import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.example.Mapper.brandMapper;
import org.example.pojo.brand;
import org.example.util.SqlSessionFactoryUtils;

public class brandService {

String resource = "mybatis-config.xml";
            InputStream inputStream = null;
            inputStream = Resources.getResourceAsStream(resource);
           SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    //调用brandMapper中的selectAll方法。
    public List<brand> selectAll(){

        //获取session
        SqlSession sqlSession = sqlSessionFactory.openSession();

        brandMapper brandMapper = sqlSession.getMapper(brandMapper.class);

        List<brand> brands = brandMapper.selectAll();

        sqlSession.close();

        return brands;
    }
}

下面让我们写展示brand信息的jsp页面：

注意：<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>，只有声明该配置，才能应用pom文件中配置的工具jstl依赖。

jstl工具中有<c:foreach> 相当于Java中的for循环和<c:if>标签相当于Java语句中的if语句。

<%--
  Created by IntelliJ IDEA.
  User: quwenhao
  Date: 2023/12/28
  Time: 17:46
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>${user.username},欢迎您</h1>

<input type="button" value="新增" id="addBrand"><br>
<hr>
<table border="1" cellspacing="0" width="800">
    <tr>
        <td>序号</td>
        <td>品牌名称</td>
        <td>企业名称</td>
        <td>排序</td>
        <td>品牌介绍</td>
        <td>状态</td>
        <td>操作</td>
    </tr>
    <c:forEach items="${brands}" var="brand" varStatus="Status">
<-- var 属性是为多个brands中的一个个体命名  varStatus是为每条信息前的序号命名，设置为index是序号从1开始递增-->
    <tr align="center">
            <%--      <td>${brand.id}</td>--%>
        <td>${Status.index}</td>
        <td>${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="#">修改</a> <a href="#">删除</a> </td>
        </c:forEach>
       
</table>

</body>
</html>

下面到了写jsp页面中信息的来源了 Servlet。新建一个Servlet

package org.example.web;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;
import java.util.List;

import org.example.pojo.brand;
import org.example.service.brandService;

@WebServlet("/brandSelectAllService")
public class brandSelectAllService extends HttpServlet {
    private brandService brandService=new brandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1调用对应的brandService方法
        List<brand> brands = brandService.selectAll();

        //2存入request对象中
        request.setAttribute("brands",brands);

        //3.转发到brand.jsp
        request.getRequestDispatcher("/brand.jsp").forward(request,response);

    }

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

在该Servlet中调用前面声明的查询数据库的方法，获取数据库信息后，在将获取的brands数据转发到brand.jsp页面中。

然后我们可以写一个index.html文件来登陆brands

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<a href="/brandSelectAllService">登陆</a>
</body>
</html>

点击登陆就会进入查询Servlet中，执行查询所有方法，然后在跳转到brands.jsp页面中展示信息。

下面来看看效果：