wen 编程最新 2024-01-31

12-基于ElementUI&Servlet的CRUD综合案例

0、综合案例功能介绍

以上是在综合案例要实现的功能。除了对数据的增删改查功能之外，还有一些复杂的功能，如批量删除，分页查询，条件查询等功能
- 批量删除功能：每条数据前都有复选框，当我们选中多条数据并点击批量删除按钮后，会发送请求到后端并删除数据库指定的多条数据
- 分页查询功能：当数据库中有很多数据的时候，我们不可能将所有的数据展示在一页里，这个时候就需要分页展示数据
- 条件查询功能：数据库量大的时候，我们需要精确的查询一些想看到的数据，这个时候就需要通过条件查询

1、查询所有功能

整体流程如下图所示

1.1、后端实现

1.1.1、dao方法实现

在com.coolman.mapper.BrandMapper接口中定义抽象方法，使用@Select注解编写SQL语句

// 查询所有品牌
    @Select("select * from brand.tb_brand order by ordered")
    List<Brand> selectAllBrands();

由于表中有些字段名和实体类中的属性名没有对应，所以要进行相关配置

方法1：在SQL语句中取别名

// 查询所有品牌
    @Select("select id, brand_name as brandName, company_name as companyName, ordered, description, status from brand.tb_brand order by ordered")
    List<Brand> selectAllBrands();

方法2：在BrandMapper.xml映射配置文件中定义结果映射，同时在使用注解开发的条件下在Mapper接口中使用ResultMap注解

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

//查询所有品牌
    @Select("select * from brand.tb_brand order by ordered")
    @ResultMap("brandResultMap")
    List<Brand> selectAllBrands();

方法3：在MyBatis配置文件中设置并开启驼峰自动命名映射

<settings>
  <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>

1.1.2、service实现

// 查询所有品牌
    public List<Brand> selectAllBrands() {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        List<Brand> brands = mapper.selectAllBrands();

        sqlSession.close();
        return brands;
    }

1.1.3、Servlet实现

package com.coolman.web.servlet;

import com.alibaba.fastjson.JSON;
import com.coolman.pojo.Brand;
import com.coolman.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("/selectAllBrandsServlet")
public class SelectAllBrandsServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里处理请求

        // 调用服务，查询所有
        List<Brand> brands = new BrandService().selectAllBrands();
//        System.out.println(brands);

        // 将List对象转换为JSON字符串，传递给前端
        String brandsJson = JSON.toJSONString(brands);

        // 解决中文乱码问题，声明字符串为JSON字符串
        response.setContentType("application/json;charset=utf-8");

        // 返回JSON字符串
        response.getWriter().print(brandsJson);
    }
}

1.2、前端实现

created() {
            axios.get("selectAllBrandsServlet").then( response => {
                // window.alert("正在请求数据");
                // console.log(response.data);
                this.tableData = response.data;
            });
        },

2、添加功能

整体流程如图所示

2.1、后端实现

2.1.1、dao方法实现

// 添加品牌
    @Insert("insert into brand.tb_brand values(null, #{brandName}, #{companyName}, #{ordered}, #{description}, #{status})")
    void addBrand(Brand brand);

2.1.2、service方法实现

// 添加品牌
    public void addBrand(Brand brand) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.addBrand(brand);

        sqlSession.commit();

        sqlSession.close();
    }

2.1.3、servlet方法实现

package com.coolman.web.servlet;

import com.alibaba.fastjson.JSON;
import com.coolman.pojo.Brand;
import com.coolman.service.BrandService;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletOutputStream;
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.io.PrintStream;

@WebServlet("/addBrandServlet")
public class AddBrandServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里处理请求

        // 获取ajax请求返回的json字符串
        // 获取请求体中的输入流
        ServletInputStream inputStream = request.getInputStream();
        // 调用JSON的api将返回的json字符串转换为实体类对象
        Brand brand = JSON.parseObject(inputStream, Brand.class);

        // 调用服务保存信息
        new BrandService().addBrand(brand);

        response.getWriter().print("ok");
    }
}

2.2、前端实现

在Vue对象中的方法属性中添加一个功能

// 添加数据
            addBrand(){
                console.log(this.brand);
                axios.post("addBrandServlet", this.brand).then(response => {
                    if (response.data == "ok") {
                        this.dialogVisible = false;
                        window.location.href = "brand.html";
                    } else {
                        window.alert("添加失败！");
                    }
                })
            },

3、删除功能

3.1、后端实现

3.1.1、dao层实现

// 删除品牌
    @Delete("delete from brand.tb_brand where id = #{id}")
    void deleteBrand(int id);

3.1.2、service层实现

// 删除品牌
    public void deleteBrand(int id) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.deleteBrand(id);

        sqlSession.commit();

        sqlSession.close();
    }

3.1.3、servlet层实现

package com.coolman.web.servlet;

import com.coolman.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;

@WebServlet("/deleteBrandServlet")
public class DeleteBrandServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里处理请求

        // 获取返回的id
        String idStr = request.getParameter("id");
        int id = Integer.parseInt(idStr);

        // 调用服务，删除该品牌
        new BrandService().deleteBrand(id);

        // 返回成功删除信息
        response.getWriter().print("ok");
    }
}

3.2、前端实现

在Vue对象的method属性中添加deleteBrandById方法，同时在html标签中的点击事件中，传递一个参数回来到方法中

<el-table-column align="center" label="操作">
                <template slot-scope="scope">
                    <el-button type="primary" @click="">修改</el-button>
                    <el-button type="danger" @click="deleteBrandById(scope.row.id)">删除</el-button>
                </template>
            </el-table-column>

// 删除数据
            deleteBrandById(id){
                // 发送ajax请求
                axios.get("deleteBrandServlet?id=" + id).then( response => {
                    if (response.data == "ok") {
                        // 删除成功，跳转回brand.html
                        window.location.href = "brand.html";
                    } else {
                        window.alert("删除失败");
                    }
                });
            },

4、修改功能

4.1、后端实现

4.1.1、dao层实现

// 修改品牌
    // 回显功能，根据id查询品牌信息
    @Select("select * from brand.tb_brand where id = #{id}")
    Brand selectBrandById(int id);
    // 修改功能
    @Update("update brand.tb_brand set brand_name = #{brandName}, company_name = #{companyName}, ordered = #{ordered}, " +
            "description = #{description},status = #{status} where id = #{id}")
    void updateBrandById(Brand brand);

4.1.2、service层实现

    // 修改品牌
    // 回显功能
    public Brand selectBrandById(int id) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        Brand brand = mapper.selectBrandById(id);

        sqlSession.close();

        return brand;
    }
    // 修改功能
    public void updateBrandById(Brand brand) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        sqlSession.getMapper(BrandMapper.class).updateBrandById(brand);

        sqlSession.commit();
        sqlSession.close();
    }

4.1.3、servlet层实现

回显功能

package com.coolman.web.servlet;

import com.alibaba.fastjson.JSON;
import com.coolman.pojo.Brand;
import com.coolman.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;

@WebServlet("/selectBrandByIdServlet")
public class SelectBrandByIdServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里处理请求

        // 接收前端返回的id
        String idStr = request.getParameter("id");
        int id = Integer.parseInt(idStr);

        // 调用服务，查询品牌信息
        Brand brand = new BrandService().selectBrandById(id);

        // 将Java对象转换成json数据，返回给前端
        String jsonString = JSON.toJSONString(brand);

        // 向前端声明返回的数据是json数据，同时更改编码格式防止编码错误
        response.setContentType("application/json;charset=utf-8");

//        System.out.println(jsonString);
        response.getWriter().print(jsonString);
    }
}

修改功能

package com.coolman.web.servlet;

import com.alibaba.fastjson.JSON;
import com.coolman.pojo.Brand;
import com.coolman.service.BrandService;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
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("/updateBrandByIdServlet")
public class UpdateBrandByIdServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里处理请求
        // 接收前端返回的json数据
        // 得到输入流
        ServletInputStream inputStream = request.getInputStream();
        // 待用JSON的API转换成JAVA对象
        Brand brand = JSON.parseObject(inputStream, Brand.class);

        // 调用服务，修改数据
        new BrandService().updateBrandById(brand);

        // 返回修改成功信息给前端
        response.getWriter().print("ok");
    }
}

4.2、前端实现

//修改数据
            // 点击修改按钮后，为了增强用户体验，添加一个数据回显功能
            selectBrandById(id){
                this.dialogVisibleUpdate = true
                // 发送ajax请求
                axios.get("selectBrandByIdServlet?id=" + id).then(response => {
                 // 接收后端返回的json数据
                 this.brand = response.data;
                 // el-switch开关的默认值必须类型也要匹配~
                 this.brand.status = this.brand.status.toString();
                 console.log(this.brand);
                });
            },
            // 执行修改语句
            updateBrandById(id){
                // 发送ajax请求
                axios.post("updateBrandByIdServlet", this.brand).then(response => {
                   if (response.data == "ok") {
                       // 跳转到brand.html页面
                       window.location.href = "brand.html";
                   }else {
                       window.alert("修改失败！")
                   }
                });
            },

5、servlet优化

5.1、背景

Web层的Servlet个数太多，不利于管理和编写
- 模块的每一个功能都需要定义一个servlet，当模块的数量多时，就很容易造成servlet泛滥。

5.2、解决方法

一个模块只定义一个servlet，模块中的每一个功能只需要在servlet中定义对应的方法，如下代码所示

@WebServlet("/brand/*")
public class BrandServlet {
    //查询所有
	public void selectAll(...) {}
    
    //添加数据
    public void add(...) {}
    
     //修改数据
    public void update(...) {}
    
    //删除删除
    public void delete(...) {}
}

5.3、思路

当发送请求至servlet，tomcat会自动调用service()方法，源码如下所示
- 我们一般在自定义的servlet中会重写doGet()和doPost()方法，当我们访问该servlet的时候会根据请求方式将请求分发给doGet()或者doPost()方法
那么可以仿照这样的请求分发的思想，在service()方法中根据具体的操作调用对应的方法
- 如：查询所有就调用selectAll()方法，添加企业信息就调用add()方法

5.4、具体实现

定义一个通用的servlet类，在定义其他的servlet是不需要继承HttpServlet，而继承我们定义的BaseServlet，在BaseServlet中调用具体servlet（如BrandServlet）中的对应方法，如下所示

BaseServlet

public class BaseServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //进行请求的分发
    }
}

BrandServlet

@WebServlet("/brand/*")
public class BrandServlet extends BaseServlet {
    //用户实现分页查询
	public void selectAll(...) {} 
    
    //添加企业信息
    public void add(...) {}
    
    //修改企业信息
    public void update(...) {}
    
    //删除企业信息
    public void delete(...) {}
}

那么如何在BaseServlet中调用对应的方法，进行请求分发呢？
- 可以规定在发送请求的时候，请求资源的二级路径（/brandServlet/selectAll）和需要调用的方法名相同，如下所示
  - 查询所有数据的路径以后就需要写成： http://localhost:8080/brand-case/brandServlet/selectAll
  - 添加数据的路径以后就需要写成： http://localhost:8080/brand-case/brandServlet/add
  - 修改数据的路径以后就需要写成： http://localhost:8080/brand-case/brandServlet/update
  - 删除数据的路径以后就需要写成： http://localhost:8080/brand-case/brandServlet/delete
- 或者给在路径中添加一个参数，值为对应的方法名称，如下所示
  - 查询所有数据的路径以后就需要写成： http://localhost:8080/brand-case/brandServlet?action=selectAll
  - …
这样的话，在BaseServlet中就需要获取到资源的二级路径作为方法名或者路径中的action参数的值，然后调用该方法

5.4.1、后端代码

BaseServlet

package com.coolman.web.servlet;

import cn.hutool.core.util.StrUtil;
import com.coolman.web.servlet.BrandServlet;

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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class BaseServlet extends HttpServlet {

    @Override
    // tomcat中的servlet每次被调用都会执行service方法
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 在这里分发请求
        // 1. 获取方法名称
        // 1.1 如果请求的URL格式为 .../brandServlet?action=selectAll

        // 那么获取方法名称则要简单很多
//        String methodName = request.getParameter("action");     // 但是在前端的ajax请求中就需要多写一些单词

        // 1.2 如果请求的URL格式为 .../brandServlet/selectAll
        // 使用工具类，获取到最后一个"/"号后面的字符串
        // 1.2.1 获取请求的URI
        String requestURI = request.getRequestURI();
        // 1.2.2 使用工具类，获取到最后一个"/"号后面的字符串
        String methodName = StrUtil.subAfter(requestURI, "/", true);

        // 2. 获取方法名称后调用方法
        // 方式1：
//        if ("selectAll".equals(methodName)) {
//            selectAll(request, response);
//        } else if ("add".equals(methodName)) {
//            add(request, response);
//        } else if ("delete".equals(methodName)) {
//            delete(request, response);
//        } else if ("update".equals(methodName)) {
//            update(request, response);
//        } //else if ...

        // 方式2: 方式1在当功能多的时候就会显地条件判断很冗余
        //  可以利用反射的方法,获取到方法,然后调用对应的方法即可
        try {
            Method method = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
            // 再让方法对象执行
            // 暴力反射获取字节码对象的时候需要去除权限(在同一个包下,protected是可以访问的)
//            method.setAccessible(true);
            method.invoke(this, request, response);
        } catch (Exception e) {
            e.printStackTrace();
        }
//        catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
//            e.printStackTrace();
//        }

    }
}

BrandServlet

package com.coolman.web.servlet;

import com.alibaba.fastjson.JSON;
import com.coolman.pojo.Brand;
import com.coolman.service.BrandService;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/brand/*") // 不带action
//@WebServlet("/brand") // 带action
public class BrandServlet extends BaseServlet {
    // 查询所有品牌
    protected void selectAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 调用服务，查询所有
        List<Brand> brands = new BrandService().selectAllBrands();
//        System.out.println(brands);

        // 将List对象转换为JSON字符串，传递给前端
        String brandsJson = JSON.toJSONString(brands);

        // 解决中文乱码问题，声明字符串为JSON字符串
        response.setContentType("application/json;charset=utf-8");

        // 返回JSON字符串
        response.getWriter().print(brandsJson);
    }

    // 添加品牌
    protected void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取ajax请求返回的json字符串
        // 获取请求体中的输入流
        ServletInputStream inputStream = request.getInputStream();
        // 调用JSON的api将返回的json字符串转换为实体类对象
        Brand brand = JSON.parseObject(inputStream, Brand.class);

        // 调用服务保存信息
        new BrandService().addBrand(brand);

        response.getWriter().print("ok");
    }

    // 删除品牌
    protected void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取返回的id
        String idStr = request.getParameter("id");
        int id = Integer.parseInt(idStr);

        // 调用服务，删除该品牌
        new BrandService().deleteBrand(id);

        // 返回成功删除信息
        response.getWriter().print("ok");
    }

    // 根据id查询品牌
    protected void selectBrandById(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收前端返回的id
        String idStr = request.getParameter("id");
        int id = Integer.parseInt(idStr);

        // 调用服务，查询品牌信息
        Brand brand = new BrandService().selectBrandById(id);

        // 将Java对象转换成json数据，返回给前端
        String jsonString = JSON.toJSONString(brand);

        // 向前端声明返回的数据是json数据，同时更改编码格式防止编码错误
        response.setContentType("application/json;charset=utf-8");

//        System.out.println(jsonString);
        response.getWriter().print(jsonString);
    }

    // 修改品牌信息
    protected void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收前端返回的json数据
        // 得到输入流
        ServletInputStream inputStream = request.getInputStream();
        // 待用JSON的API转换成JAVA对象
        Brand brand = JSON.parseObject(inputStream, Brand.class);

        // 调用服务，修改数据
        new BrandService().updateBrandById(brand);

        // 返回修改成功信息给前端
        response.getWriter().print("ok");
    }

}

注意事项

BaseServlet和BrandServlet要放在同一个包下，否则因为BrandServlet中的方法全都是protected修饰的方法，必须要设置取出权限才可调用
- method.setAccessible(true);

7、批量删除

7.1、后端实现

7.1.1、dao层实现

BrandMapper.java

// 批量删除
    void deleteByIds(@Param("ids") int[] ids);

BrandMapper.xml

<delete id="deleteByIds">
        delete from brand.tb_brand where id in
        <foreach collection="ids" separator="," open="(" close=")" item="id">
            #{id}
        </foreach>
    </delete>

7.1.2、service层实现

    // 批量删除功能
    public void deleteByIds(int[] ids) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession(true);
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.deleteByIds(ids);

        sqlSession.close();
    }

7.1.3、web层servlet实现

    // 批量删除
    protected void deleteByIds(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收前端返回的id数组
        ServletInputStream inputStream = request.getInputStream();
        int[] ids = JSON.parseObject(inputStream, int[].class);

        // 调用服务
        new BrandService().deleteByIds(ids);

        // 返回成功信息
        response.getWriter().print("ok");
    }

7.2、前端实现

body中的标签绑定好事件后，执行事件的方法

       // 批量删除数据
       deleteBatch() {
           this.$confirm("确定要删除吗?","提示", {
               confirmButtonText: "确定",
               cancelButtonText: "取消",
               type: "warning"
           }).then( () => {
               // 点击确定按钮后要执行的操作
               // this.$message({
               //     message: "删除成功!",
               //     type: "success"
               // });
               let ids = [];
               for (let i = 0; i < this.multipleSelection.length; i++) {
                   // ids[i] = this.multipleSelection[i].id;
                   ids.push(this.multipleSelection[i].id);
               }
               console.log(ids);
               axios.post("brand/deleteByIds", ids).then( response => {
                   if (response.data == "ok") {
                       window.location.href = "brand.html";
                   } else {
                       this.$message({
                           message: "删除失败!",
                           type: "error"
                       });
                   }
               });
           });
       },

8、分页查询

8.1、后端实现

8.1.1、dao层实现

// 分页查询
    //select * from ... limit 起始索引, 每页条数
//    select * from tb_brand limit 0, 5;  // 第一页
//
//    select * from tb_brand limit 5, 5;  // 第二页
//
//    select * from tb_brand limit 10, 5; // 第三页

    //select * from ... limit (起始索引 - 1) * 每页条数, 每页条数
    @Select("select * from brand.tb_brand limit #{currentPage}, #{pageSize}")
    List<Brand> selectBrandByPage(@Param("currentPage") int currentPage, @Param("pageSize") int pageSize);
    // 页码左边需要的总条数
    @Select("select count(*) from brand.tb_brand")
    Integer selectSumCount();

8.1.2、service层实现

    // 分页功能
    public PageBean<Brand> selectBrandByPage(int currentPage, int pageSize) {
        //select * from ... limit (起始索引 - 1) * 每页条数, 每页条数
        currentPage = (currentPage - 1) * pageSize;

        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        List<Brand> brands = mapper.selectBrandByPage(currentPage, pageSize);
        int totalCount = mapper.selectSumCount();

        sqlSession.close();

        return new PageBean<Brand>(totalCount, brands);
    }

8.1.3、web层servlet实现

    // 处理分页请求
    protected void selectBrandByPage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收前端返回的页码数
        // pageSize
        int pageSize = Integer.parseInt(request.getParameter("pageSize"));

        // currentPage
        int currentPage = Integer.parseInt(request.getParameter("currentPage"));

        // 调用服务
        PageBean<Brand> pageBean = new BrandService().selectBrandByPage(currentPage, pageSize);

        // 返回数据
        String string = JSON.toJSONString(pageBean);
        response.setContentType("application/json;charset=utf-8");
        response.getWriter().print(string);
    }

8.2、前端实现

created()函数

created() {
            axios.get("brand/selectBrandByPage?currentPage=" + this.currentPage + "&pageSize=" + this.pageSize).then( response => {
                // window.alert("正在请求数据");
                // console.log(response.data);
                this.totalCount = response.data.totalCount;
                this.tableData = response.data.list;
            });
        }

handleSizeChange(val)函数(每一页的数据量)

handleSizeChange(val) {
                console.log(`每页 ${val} 条`);
                this.pageSize = val;
                axios.get("brand/selectBrandByPage?currentPage=" + this.currentPage + "&pageSize=" + this.pageSize).then( response => {
                    // window.alert("正在请求数据");
                    // console.log(response.data);
                    this.tableData = response.data.list;
                });

            }

handleCurrentChange(val)函数(当前页码)

handleCurrentChange(val) {
                console.log(`当前页: ${val}`);
                this.currentPage = val;
                axios.get("brand/selectBrandByPage?currentPage=" + this.currentPage + "&pageSize=" + this.pageSize).then( response => {
                    // window.alert("正在请求数据");
                    // console.log(response.data);
                    this.tableData = response.data.list;
                });
            }

9、条件查询

9.1、后端实现

9.1.1、dao层实现

Mapper接口

// 多条件查询
    List<Brand> selectBrandByCondition(@Param("brand") Brand brand, @Param("currentPage") int currentPage, @Param("pageSize") int pageSize);
    // 查询结果记录数
    int selectSearchCount(Brand brand);

Mapper映射文件

<select id="selectBrandByCondition" resultMap="brandResultMap">
        select * from brand.tb_brand
        <where>
            <!-- 当状态码设置为0或1的时候,很容易出现框架自动转换成false或true的情况;可以看作一个小bug -->
                <!-- 当传入的是int型的数字 0 时，mybatis会把它当成空字符串
                     status != "", 0 != ""  ==>  "" != ""
                -->
            <if test="brand.status != null">
                status = #{brand.status}
            </if>
            <if test="brand.brandName != null and brand.brandName != """>
                and brand_name like #{brand.brandName}
            </if>
            <if test="brand.companyName != null and brand.companyName != """>
                and company_name like #{brand.companyName}
            </if>
        </where>
        order by ordered limit #{currentPage}, #{pageSize}
    </select>

    <select id="selectSearchCount" resultType="java.lang.Integer">
        select count(*) from brand.tb_brand
        <where>
            <if test="status != null">
                status = #{status}
            </if>
            <if test="brandName != null and brandName != """>
                and brand_name like #{brandName}
            </if>
            <if test="companyName != null and companyName != """>
                and company_name like #{companyName}
            </if>
        </where>
    </select>

9.1.2、service层实现

    // 多条件查询
    public PageBean<Brand> selectBrandByCondition(Brand brand, int currentPage, int pageSize) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        if (brand.getBrandName() != null && brand.getBrandName().length() > 0) {
            brand.setBrandName("%" + brand.getBrandName() + "%");
        }
        if (brand.getCompanyName() != null && brand.getCompanyName().length() > 0) {
            brand.setCompanyName("%" + brand.getCompanyName() + "%");
        }

        currentPage = (currentPage - 1) * pageSize;
        List<Brand> brands = mapper.selectBrandByCondition(brand, currentPage, pageSize);
      	int count = mapper.selectSearchCount(brand);
        sqlSession.close();
      	return new PageBean<>(count, brands);
    }

9.1.3、web层servlet实现

    // 处理搜索请求
    protected void selectBrandByCondition(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收前端返回的数据
        int currentPage = Integer.parseInt(request.getParameter("currentPage"));
        int pageSize = Integer.parseInt(request.getParameter("pageSize"));

        ServletInputStream inputStream = request.getInputStream();
        Brand brand = JSON.parseObject(inputStream, Brand.class);

        System.out.println("brand = " + brand);

        // 调用服务
        PageBean<Brand> brands = new BrandService().selectBrandByCondition(brand, currentPage, pageSize);

        // 返回数据
        String string = JSON.toJSONString(brands);
        response.setContentType("application/json;charset=utf-8");
        response.getWriter().print(string);
    }

9.2、前端实现

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>商品列表</title>
    <style>
        .el-table .warning-row {
            background: oldlace;
        }

        .el-table .success-row {
            background: #f0f9eb;
        }
    </style>

</head>
<body>
<div id="app">

    <!--搜索表单-->
    <el-form :inline="true" v-model="brand" class="demo-form-inline">

        <el-form-item label="当前状态">
            <el-select v-model="brand.status" placeholder="当前状态">
                <el-option label="启用" value="1"></el-option>
                <el-option label="禁用" value="0"></el-option>
            </el-select>
        </el-form-item>

        <el-form-item label="企业名称">
            <el-input v-model="brand.companyName" placeholder="企业名称"></el-input>
        </el-form-item>

        <el-form-item label="品牌名称">
            <el-input v-model="brand.brandName" placeholder="品牌名称"></el-input>
        </el-form-item>

        <el-form-item>
            <el-button type="primary" @click="onSubmit()">查询</el-button>
        </el-form-item>
    </el-form>

    <!--按钮-->
    <el-row>
        <el-button type="danger" plain @click="deleteBatch()">批量删除</el-button>
        <el-button type="primary" plain @click="dialogVisibleAdd = true">新增</el-button>
    </el-row>

    <!--添加数据对话框表单-->
    <el-dialog
            title="添加品牌"
            :visible.sync="dialogVisibleAdd"
            width="30%"
            >

        <el-form ref="form" :model="brand" label-width="80px">
            <el-form-item label="品牌名称">
                <el-input v-model="brand.brandName"></el-input>
            </el-form-item>

            <el-form-item label="企业名称">
                <el-input v-model="brand.companyName"></el-input>
            </el-form-item>

            <el-form-item label="排序">
                <el-input v-model="brand.ordered"></el-input>
            </el-form-item>

            <el-form-item label="备注">
                <el-input type="textarea" v-model="brand.description"></el-input>
            </el-form-item>

            <el-form-item label="状态">
                <el-switch v-model="brand.status"
                           active-value="1"
                           inactive-value="0"
                ></el-switch>
            </el-form-item>
                    <el-form-item>
              <el-button type="primary" @click="addBrand">提交</el-button>
              <el-button @click="dialogVisibleAdd = false">取消</el-button>
          </el-form-item>
      </el-form>

  </el-dialog>

  <!--修改数据对话框表单-->
  <el-dialog
          title="编辑品牌"
          :visible.sync="dialogVisibleUpdate"
          width="30%"
  >

      <el-form ref="form" :model="brand" label-width="80px">
          <el-form-item label="品牌名称">
              <el-input v-model="brand.brandName"></el-input>
          </el-form-item>

          <el-form-item label="企业名称">
              <el-input v-model="brand.companyName"></el-input>
          </el-form-item>

          <el-form-item label="排序">
              <el-input v-model="brand.ordered"></el-input>
          </el-form-item>

          <el-form-item label="备注">
              <el-input type="textarea" v-model="brand.description"></el-input>
          </el-form-item>

          <el-form-item label="状态">
              <el-switch
                      v-model="brand.status"
                      active-value="1"
                      inactive-value="0"
              ></el-switch>

          </el-form-item>
                  <el-form-item>
              <el-button type="primary" @click="update()">提交</el-button>
              <el-button @click="dialogVisibleUpdate = false">取消</el-button>
          </el-form-item>
      </el-form>

  </el-dialog>

  <!--表格-->
  <template>
      <el-table
              :data="tableData"
              style="width: 100%"
              :row-class-name="tableRowClassName"
              @selection-change="handleSelectionChange"
      >
          <el-table-column
                  type="selection"
                  width="55">
          </el-table-column>
          <el-table-column
                  type="index"
                  width="50">
          </el-table-column>

          <el-table-column
                  prop="brandName"
                  label="品牌名称"
                  align="center"
          >
          </el-table-column>
          <el-table-column
                  prop="companyName"
                  label="企业名称"
                  align="center"
          >
          </el-table-column>
          <el-table-column
                  prop="ordered"
                  align="center"
                  label="排序">
          </el-table-column>
          <el-table-column
                  prop="description"
                  align="center"
                  label="描述">
          </el-table-column>
          <el-table-column
                  prop="status"
                  align="center"
                  label="当前状态">
              <template slot-scope="scope">
                  <el-tag type="success" v-if="scope.row.status=="1"">启用</el-tag>
                  <el-tag type="danger" v-else>禁用</el-tag>
              </template>
          </el-table-column>

          <el-table-column align="center" label="操作">
              <template slot-scope="scope">
                  <el-button type="primary" @click="selectBrandById(scope.row.id)">修改</el-button>
                  <el-button type="danger" @click="deleteBrandById(scope.row.id)">删除</el-button>
              </template>
          </el-table-column>

      </el-table>
  </template>

  <!--分页工具条-->
  <el-pagination
          @size-change="handleSizeChange"
          @current-change="handleCurrentChange"
          :current-page="currentPage"
          :page-sizes="[5, 10, 15, 20]"
          :page-size="pageSize"
          layout="total, sizes, prev, pager, next, jumper"
          :total="totalCount">
  </el-pagination>
    </div>

  <script src="js/vue.js"></script>

  <script src="./js/axios-0.18.0.js"></script>

  <script src="element-ui/lib/index.js"></script>

  <link rel="stylesheet" href="element-ui/lib/theme-chalk/index.css">

  <script>
  new Vue({
      el: "#app",
      created() {
          this.selectAll();
      },
      data() {
          return {
              // 当前页码
              currentPage: 1,
              // 总数据数
              totalCount: 0,
              // 每一页的数据数量
              pageSize: 5,

              // 搜索框

              // 添加数据对话框是否展示的标记
              dialogVisibleAdd: false,
              // 修改数据对话框是否展示的标记
              dialogVisibleUpdate: false,

              // 品牌模型数据
              brand: {
                  status: "",
                  brandName: "",
                  companyName: "",
                  id:"",
                  ordered:"",
                  description:""
              },
              // 复选框选中数据集合
              multipleSelection: [],
              // 表格数据
              tableData: [],
              // 页码数
          }
      },
      methods: {
          tableRowClassName({row, rowIndex}) {
              if (rowIndex === 1) {
                  return "warning-row";
              } else if (rowIndex === 3) {
                  return "success-row";
              }
              return "";
          },
          // 复选框选中后执行的方法
          handleSelectionChange(val) {
              this.multipleSelection = val;
              console.log(this.multipleSelection)
          },
          // 查询方法
          onSubmit() {
              // console.log("当前页码:" + this.currentPage)
              // console.log("每页数量:" + this.pageSize)
              // console.log("搜索部分信息:")
              // console.log(this.brand)
              this.selectAll();
          },
          selectAll() {
              axios.post("brand/selectBrandByCondition?currentPage=" + this.currentPage + "&pageSize=" + this.pageSize,
                  this.brand
              ).then( response => {
                  // window.alert("正在请求数据");
                  console.log(response.data);
                  this.totalCount = response.data.totalCount;
                  this.tableData = response.data.list;
              });
          },

          // 添加数据
          addBrand(){
              console.log(this.brand);
              axios.post("brand/add", this.brand).then(response => {
                  if (response.data == "ok") {
                      this.dialogVisible = false;
                      window.location.href = "brand.html";
                  } else {
                      window.alert("添加失败！");
                  }
              })
          },

          // 删除数据
          deleteBrandById(id){
              // 发送ajax请求
              axios.get("brand/delete?id=" + id).then( response => {
                  if (response.data == "ok") {
                      // 删除成功，跳转回brand.html
                      window.location.href = "brand.html";
                  } else {
                      window.alert("删除失败");
                  }
              });
          },

          //修改数据
          // 点击修改按钮后，为了增强用户体验，添加一个数据回显功能
          selectBrandById(id){
              this.dialogVisibleUpdate = true
              // 发送ajax请求
              axios.get("brand/selectBrandById?id=" + id).then(response => {
               // 接收后端返回的json数据
               this.brand = response.data;
               // el-switch开关的默认值必须类型也要匹配~
               this.brand.status = this.brand.status.toString();
               console.log(this.brand);
              });
          },
          // 执行修改语句
          update(){
              // 发送ajax请求
              axios.post("brand/update", this.brand).then(response => {
                 if (response.data == "ok") {
                     // 跳转到brand.html页面
                     window.location.href = "brand.html";
                 }else {
                     window.alert("修改失败！")
                 }
              });
          },

          // 批量删除数据
          deleteBatch() {
              this.$confirm("确定要删除吗?","提示", {
                  confirmButtonText: "确定",
                  cancelButtonText: "取消",
                  type: "warning"
              }).then( () => {
                  // 点击确定按钮后要执行的操作
                  // this.$message({
                  //     message: "删除成功!",
                  //     type: "success"
                  // });
                  let ids = [];
                  for (let i = 0; i < this.multipleSelection.length; i++) {
                      // ids[i] = this.multipleSelection[i].id;
                      ids.push(this.multipleSelection[i].id);
                  }
                  console.log(ids);
                  axios.post("brand/deleteByIds", ids).then( response => {
                      if (response.data == "ok") {
                          window.location.href = "brand.html";
                      } else {
                          this.$message({
                              message: "删除失败!",
                              type: "error"
                          });
                      }
                  });
              });
          },

          //分页
          handleSizeChange(val) {
              console.log(`每页 ${val} 条`);
              this.pageSize = val;
              this.selectAll();

          },
          handleCurrentChange(val) {
              console.log(`当前页: ${val}`);
              this.currentPage = val;
              this.selectAll();
          },

      }
  })
      </script>
  </body>
  </html>

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