ssm一对多步骤

1.使用一对多，取到两表之前或多表之间的值
（1）第一步实体类(三表关系)
（a）BigType.java

             //商品分类--大
            public class BigType {
                private int id;//编号
                private String name;//类型名称
                private String remarks;//别名
                //一对多--one端
                private Set<SmallType> smallTypes = new HashSet<SmallType>();
                private Set<Product> products = new HashSet<Product>();
                //封装
            }

(b)SmallType.java

         //商品分类--小
        public class SmallType {
            private int id;//编号
            private String name;//类型名称
            private String remarks;//别名
            private int bigTypeId;//商品类型ID-大
            private BigType bigType;//many端
            private Set<Product> products = new HashSet<Product>();            
            //封装
        }

(c)Product.java

 public class Product {
                private int id;//编号
                private String description;//商品详情
                private int hot;//热门推荐，1为热门，0不是热门
                private Date hotTime;//热门时间
                private String name;//商品名称
                private int price;//商品价格
                private String proPic;//商品图片
                private int specialPrice;//今日特价，1为特价，0不是特价
                private Date specialPriceTime;//特价时间
                private int stock;//库存
                private int bigTypeId;//商品类型id-大
                private int smallTypeId;//商品类型id-小

                private SmallType smallType;
                private BigType bigType;
                //封装
            }

（2）第二步在mapper.xml文件中填写
（a）BigTypeMapper.xml文件

  <resultMap type="BigType" id="bigTypeList">
            <!-- 双向必须配置该表主键  不然显示不出 -->
                <result property="id" column="id"/>
                <collection property="smallTypes" column="id" select="cn.jbit.dao.SmallTypeDao.getSmallTypeByBigTypeId"></collection>
                <collection property="products" column="id" select="cn.jbit.dao.ProductDao.getBigTypeByBigTypeId"></collection>
            </resultMap>
            
            
            <!-- 双向一定都要写查询语句 -->
            <select id="getBigTypeById" resultMap="bigTypeList">
                select * from t_bigtype where id = #{id}
            </select>

（b）SmallTypeMapper.xml 文件

  <resultMap type="SmallType" id="smallTypeList">
                <association property="bigType" column="bigTypeId" select="cn.jbit.dao.BigTypeDao.getBigTypeById"></association>
                <!-- 多对一的关联关联复杂类型association  column="bigTypeId"外键 -->
            </resultMap>
            
            <resultMap type="SmallType" id="smList">
            <!-- 双向必须配置该表主键  不然显示不出 -->
                <result property="id" column="id"/>
                <collection property="products" column="id" select="cn.jbit.dao.ProductDao.getProductBySmallTypeId"></collection>
            </resultMap>
                
            <!-- 双向一定都要写查询语句 -->
            <select id="getSmallTypeByBigTypeId" resultMap="smallTypeList">
                select * from t_smalltype where bigTypeId=#{bigTypeId}
            </select>
            <select id="getSmallTypeById" resultMap="smList">
                select * from t_smalltype where id=#{id}
            </select>

(c)ProductMapper.xml文件

<resultMap type="Product" id="productlist">
            <association property="smallType" column="smallTypeId" select="cn.jbit.dao.SmallTypeDao.getSmallTypeById"></association>
            <association property="bigType" column="bigTypeId" select="cn.jbit.dao.BigTypeDao.getBigTypeById"></association>
            <!-- 多对一的关联关联复杂类型association  column="bigTypeId"外键 -->
            </resultMap>
            
            <select id="getProductBySmallTypeId" resultMap="productlist">
                SELECT * FROM t_product WHERE smallTypeId=#{smallTypeId}
            </select>
            <select id="getBigTypeByBigTypeId" resultMap="productlist">
                SELECT * FROM t_product WHERE bigTypeId=#{bigTypeId}
            </select>

（3）第三步 cn.jbit.dao的文件中(文件的方法与mapper一一对应)
（a）BigTypeDao.java

 public interface BigTypeDao {                            
                BigType getBigTypeById(int id);//一对多商品表或小类表
            }

（b）SmallTypeDao.java

  public interface SmallTypeDao {    
                SmallType getSmallTypeByBigTypeId(int bigTypeId);//多对一大类表
                SmallType getSmallTypeById(int id);//一对多商品表
            }

（c）ProductDao.java

   public interface ProductDao {                
                Product getProductBySmallTypeId(int smallTypeId);                
                Product getBigTypeByBigTypeId(int bigTypeId);
            }

猜你喜欢