笔记|Mybatis小练习
建表语句
CREATE TABLE category(
cid VARCHAR(32) PRIMARY KEY,
cname VARCHAR(50),
parent_id VARCHAR(32),
`desc` VARCHAR(100)
);
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c100','童书','0','一级分类');
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c200','电子书','0','一级分类');
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c101','中国儿童文学','c100','二级分类');
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c102','婴儿读物','c100','二级分类');
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c201','武侠小说','c200','二级分类');
INSERT INTO category(cid,cname,parent_id,`desc`) VALUES('c202','侦探推理','c200','二级分类');
CREATE TABLE book(
bid VARCHAR(32) PRIMARY KEY,
title VARCHAR(50),
price DOUBLE(6,2),
author VARCHAR(50),
cid VARCHAR(32)
);
INSERT INTO book(bid,title,price,author,cid) VALUES('b001','学会管自己（歪歪兔独立成长童话）',64.00,'陈梦敏','c101');
INSERT INTO book(bid,title,price,author,cid) VALUES('b002','写给儿童的中国历史',177.50,'陈卫平','c101');
INSERT INTO book(bid,title,price,author,cid) VALUES('b003','小鸡球球触感玩具书',125.00,'[日]入山智','c102');
INSERT INTO book(bid,title,price,author,cid) VALUES('b004','天龙八部',12.00,'金庸','c201');
INSERT INTO book(bid,title,price,author,cid) VALUES('b005','朱贞木短篇小说集(全套装共8册)',103,'朱贞木','c201');
INSERT INTO book(bid,title,price,author,cid) VALUES('b006','笑傲江湖(新修版)一',1200,'金庸','c201');
INSERT INTO book(bid,title,price,author,cid) VALUES('b007','解忧杂货店',19.99,'（日）东野圭吾','c202');
INSERT INTO book(bid,title,price,author,cid) VALUES('b008','三口棺材',8.99,'（美）约翰·迪克森·卡尔','c202');
实现功能
查询一级分类，同时查询二级分类，以及查询二级分类下的所有图书
代码实现 domain
@Entity(name = "book")
public class Book {
@Id
private String bid;
private String title;
private Double price;
private String author;
private String cid;
@Override
public String toString() {
return "Book{" +
"bid='" + bid + '\'' +
", title='" + title + '\'' +
", price=" + price +
", author='" + author + '\'' +
", cid='" + cid + '\'' +
'}';
}public Book(String bid, String title, Double price, String author, String cid) {
this.bid = bid;
this.title = title;
this.price = price;
this.author = author;
this.cid = cid;
}public Book() {
}public String getBid() {
return bid;
}public void setBid(String bid) {
this.bid = bid;
}public String getTitle() {
return title;
}public void setTitle(String title) {
this.title = title;
}public Double getPrice() {
return price;
}public void setPrice(Double price) {
this.price = price;
}public String getAuthor() {
return author;
}public void setAuthor(String author) {
this.author = author;
}public String getCid() {
return cid;
}public void setCid(String cid) {
this.cid = cid;
}
【笔记|Mybatis小练习】}
@Entity(name = "category")
public class Category {
@Id
private String cid;
private String cname;
private String parent_id;
private String desc;
//一对多
private ArrayList categoriesList =new ArrayList<>();
private ArrayList booksList =new ArrayList<>();
@Override
public String toString() {
return "Category{" +
"cid='" + cid + '\'' +
", cname='" + cname + '\'' +
", parent_id='" + parent_id + '\'' +
", desc='" + desc + '\'' +
", categoriesList=" + categoriesList +
", booksList=" + booksList +
'}';
}public Category(String cid, String cname, String parent_id, String desc) {
this.cid = cid;
this.cname = cname;
this.parent_id = parent_id;
this.desc = desc;
}public ArrayList getCategoriesList() {
return categoriesList;
}public void setCategoriesList(ArrayList categoriesList) {
this.categoriesList = categoriesList;
}public ArrayList getBooksList() {
return booksList;
}public void setBooksList(ArrayList booksList) {
this.booksList = booksList;
}public Category() {
}public String getCid() {
return cid;
}public void setCid(String cid) {
this.cid = cid;
}public String getCname() {
return cname;
}public void setCname(String cname) {
this.cname = cname;
}public String getParent_id() {
return parent_id;
}public void setParent_id(String parent_id) {
this.parent_id = parent_id;
}public String getDesc() {
return desc;
}public void setDesc(String desc) {
this.desc = desc;
}
}
mapper BookMapper
public interface BookMapper {
public Book book(@Param("cid")String cid);
}
BookMapper.xml
select * from book where cid=#{cid}
Category
public interface CategoryMapper {
public ListSelectById2(@Param("cid")String cid);
public ListSelectById(@Param("cid")String cid);
public List SelectAll();
}
Category.xml
select * from category as c where c.parent_id=#{cid}
select * from category as c1 where c1.parent_id='0'
Main
public static void main(String[] args) {
CategoryMapper categoryMapper = MyBatisUtils.getMapper(CategoryMapper.class);
List list = categoryMapper.SelectAll();
list.forEach(System.out::println);
}
总结:一级和二级自表关联简称套娃
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