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（一）结构结构说明

book表: category表: evaluation表: member表: member_read_state表: user表:

（二）开发图书分类接口

1.创建entity

@TableName("category")
public class Category {
    @TableId(type = IdType.AUTO)
    private Long categoryId;
    private String categoryName;

    public Long getCategoryId() {
        return categoryId;
    }

    public void setCategoryId(Long categoryId) {
        this.categoryId = categoryId;
    }

    public String getCategoryName() {
        return categoryName;
    }

    public void setCategoryName(String categoryName) {
        this.categoryName = categoryName;
    }

    @Override
    public String toString() {
        return "Category{" +
                "categoryId=" + categoryId +
                ", categoryName='" + categoryName + ''' +
                '}';
    }
}

代码说明:

• @TableName:实体类对应的表名
• @TableId(type = IdType.AUTO):对应数据表主键自增ID
• private Long categoryId:对应数据表字段（一般情况下，整型默认采用Long类型）
• toString:方便控制台输出返回值

2.定义interface类 CategoryService

package com.imooc.reader.service;

import com.imooc.reader.entity.Category;

import java.util.List;

public interface CategoryService {
    public List<Category> selectAll();
}

代码说明:

• interface:定义接口
• selectAll：定义获取图书分类的方法

3.定义mapper接口类CategoryMapper

package com.imooc.reader.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.imooc.reader.entity.Category;

public interface CategoryMapper extends BaseMapper<Category> {
}

代码说明：

• BaseMapper:继承BaseMapper
• BaseMapper<Category>:范型Category

4.定义xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.imooc.reader.mapper.CategoryMapper">

</mapper>

代码说明：这个xml文件用来写相关的sql的增删改查语句

5.新增impl实现包并且新增categoryServiceImpl

package com.imooc.reader.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.imooc.reader.entity.Category;
import com.imooc.reader.mapper.CategoryMapper;
import com.imooc.reader.service.CategoryService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.util.List;
@Service("categoryService")
@Transactional(propagation = Propagation.NOT_SUPPORTED,readOnly = true)
public class CategoryServiceImpl implements CategoryService {
    @Resource
    CategoryMapper categoryMapper;
    @Override
    public List<Category> selectAll() {
        List<Category> list = categoryMapper.selectList(new QueryWrapper<Category>());
        return list;
    }
}

代码说明

• @Service("categoryService"):声明service
• @Transactional(propagation = Propagation.NOT_SUPPORTED,readOnly = true):不开启事物，只读，因为我们只是做查询操作
• implements CategoryService:实现CategoryService
• selectAll：实现方法
• categoryMapper.selectList(new QueryWrapper<Category>()):因为我们不需要查询条件，所以是空查询

6.新增测试用例

查询出对应的数据