Mybatis Inheritance Mappings

Inheritance Mappings

There are three kinds of mappings in hibernate to create a table table generating tables

MyBatis Database design using a table-based approach

Where Eye_color field is the cat private attribute Fur_color for the dog private property

- entity class

public class Animal implements Serializable {
    private  static  final long Serializable = 1L;
    Private Integer ID;
    private String name;

    Public Integer getId () {
        return ID;
    }

    public void SetId (Integer id) {
        this.id = ID;
    }

    Public String GetName () {
        return name;
    }

    public void SetName (String name) {
        this.name = name;
    }

    @Override public
    String toString () {
        return "animal{" +
                "id=" + ID +
                ", name= ' + name + ' + ' +
                ' }';
    }
}

Cat Class

public class Cat extends  Animal {
    private String eyecolor;

    Public String Geteyecolor () {
        return eyecolor;
    }

    public void Seteyecolor (String eyecolor) {
        this.eyecolor = Eyecolor;
    }

    @Override public
    String toString () {
        return super.tostring () + "cat{" +
                "eyecolor=" + eyecolor + ' \ ' +'}';
    }
}

Dog Class

public class Dog extends  Animal {
    private String furcolor;

    Public String Getfurcolor () {
        return furcolor;
    }

    public void Setfurcolor (String furcolor) {
        this.furcolor = Furcolor;
    }

    @Override public
    String toString () {
        return super.tostring () + "dog{" +
                "furcolor=" + furcolor + ' \ ' +< c29/> '} ';
    }
}

configuration file

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="jdbc.properties"/>   
    <typeAliases>
        <package name="com.bjlemon.mybatis.domian"/>
        <package name="com.bjlemon.mybatis.vo"/>
    </typeAliases>
    <environments default="mybatis_1">
        <environment id="mybatis_1">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <package name="com.bjlemon.mybatis.mapper"></package>
    </mappers>
</configuration>

Mapper Interface

void Savecat (cat cat);
    void Savedog (dog dog);

    /** *
     polymorphic query
     * @param ID
     * @return *
    /Animal Finbyid (Integer ID);

Service Layer

Public interface Animalservice {
    public  void Addanimal (Animal Animal);
    Animal Findanimalbyid (Integer ID);
}

public class AnimalServiceImpl implements AnimalService {
    @Override
    public void addAnimal(Animal animal) {
        SqlSession sqlSession = null;
        Cat cat = null;
        Dog dog =null;
        try{
            sqlSession = MybatisUtils.getSqlSession();
            AnimalMapper mapper = sqlSession.getMapper(AnimalMapper.class);
            if (animal instanceof Cat){
                cat = (Cat) animal;
                mapper.saveCat(cat);
            }else if (animal instanceof  Dog){
                dog = (Dog) animal;
                mapper.saveDog(dog);
            }
            sqlSession.commit();
        }catch (Exception e){
            e.printStackTrace();
            sqlSession.rollback(); // 异常则回滚
        }finally {
            MybatisUtils.clolseSqlSession();
        }
    }

    @Override
    public Animal findAnimalById(Integer id) {
        SqlSession sqlSession = null;
        Cat cat = null;
        Dog dog = null;
        try {
            sqlSession = MybatisUtils.getSqlSession();
            AnimalMapper mapper = sqlSession.getMapper(AnimalMapper.class);
            Animal animal = mapper.finById(id);
            if (animal instanceof Cat) {
                cat = (Cat) animal;
                return  cat;
            } else if (animal instanceof Dog) {
                dog = (Dog) animal;
                return  dog;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            MybatisUtils.clolseSqlSession();
        }
        return  null;
    }

}

Entity mapping File

<? 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.bjlemon.mybatis.mapper.AnimalMapper">

    <insert id = "saveCat" parameterType = "Cat">
        INSERT INTO
          mybatis_in_action_adv_animal (animal_id, animal_name, eye_color, fur_color, animal_type)
        VALUES
            (null, # {name}, # {eyeColor}, null, 'C');
    </ insert>

    <insert id = "saveDog" parameterType = "Dog">
        INSERT INTO
        mybatis_in_action_adv_animal (animal_id, animal_name, eye_color, fur_color, animal_type)
        VALUES
        (null, # {name}, null, # {furColor}, 'D');
    </ insert>

    <!-

    discriminator: the discriminator encapsulates the result differently according to the returned animal_type field
    javaType: field type
    column: field name used for identification
    case: judged value
    ->
    <resultMap id = "AnimalRM" type = "Animal">
        <id property = "id" column = "animal_id" />
        <result property = "name" column = "animal_name" />
        <discriminator javaType = "string" column = "animal_type">
            <case value = "C" resultMap = "CatRM" />
            <case value = "D" resultMap = "DogRM" />
        </ discriminator>
    </ resultMap>
    <resultMap id = "CatRM" type = "Cat" extends = "AnimalRM">
        <result property = "eyeColor" column = "eye_color" />
    </ resultMap>
    <resultMap id = "DogRM" type = "Dog" extends = "AnimalRM">
        <result property = "furColor" column = "fur_color" />
    </ resultMap>
    <select id = "finById" resultMap = "AnimalRM">
        SELECT
          *
        FROM
            mybatis_in_action_adv_animal
        WHERE
            animal_id = # {id}
    </ select>
</ mapper>