Question

在我的Spring Boot项目中，我正在使用MyBatis。我想知道如何使用一对一映射以及如何为映射类创建POJO。这是我使用过的SQL转储：

CREATE TABLE IF NOT EXISTS LANG(
ID  BIGINT(10) NOT NULL AUTO_INCREMENT,     
CODE VARCHAR(3) UNIQUE,
NAME VARCHAR(150),
PRIMARY KEY (ID)
);

CREATE TABLE IF NOT EXISTS PROVINCE(
ID  BIGINT(10) NOT NULL AUTO_INCREMENT, 
CODE VARCHAR(10) UNIQUE,        
NAME VARCHAR(200),
LANG_CODE VARCHAR(3),
PRIMARY KEY (ID),
FOREIGN  KEY(LANG_CODE) REFERENCES LANG(CODE)
);

和POJO是，

Language.java

public class Language {

    private long id;

    private String code;

    private String name;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getName() {
        return name;
    }

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

省

public class Province {

    private long id;

    private String code;

    private String name;

    private String lang_code;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getName() {
        return name;
    }

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

    public String getLang_code() {
        return lang_code;
    }

    public void setLang_code(String lang_code) {
        this.lang_code = lang_code;
    }
}

Answer 1

你应该改变你的实体省包括语言属性而不是重复它，它将是下一个：

    public class Province {

        private long id;

        private Language language;

        public long getId() {
            return id;
        }

        public void setId(long id) {
            this.id = id;
        }

        public Language getLanguage() {
            return language;
        }

        public void setLanguage(Language language) {
            this.language = language;
        } 
    }

另一方面，您需要使用语言选择操作创建Mapper，然后选择要绑定的省份。您可以使用注释查看下一个示例：

public interface MapperProvince {

    @Select("select * from PROVINCE")
    @Results({
        @Result(id=true, property = "id", column = "ID"),
        @Result(property="language", column="LANG_CODE",
        one=@One(select="com.example.MapperProvince.findByCode"))
      })
    public List<Province> findAll();

    @Select("select * from PROVINCE where ID = {id}")
    @Results({
        @Result(id=true, property = "id", column = "ID"),
        @Result(property="language", column="LANG_CODE",
        one=@One(select="com.example.MapperProvince.findByCode"))
      })
    public Province findById(long id);


    @Select("select * from LANGUAGE where CODE = {code}")
    @Results({
        @Result(id=true, property = "id", column = "id"),
        @Result(property = "code", column = "code"),
        @Result(property = "name", column = "name")
      })
    public Language findByCode(String code);

}

如您所见，有一个语言操作按代码搜索，它在Table Province中链接。另一方面，当您搜索省时，您的语言属性的结果应该调用语言findByCode操作链接两者。我举了一个例子，搜索所有省份或只是通过ID。

Answer 2

使用mybatis-spring-boot-starter（https://github.com/mybatis/spring-boot-starter）

进行设置

LanguageMapper.java

@Mapper
public class LanguageMapper{
   List<Language> queryLang();
}

LanguageMapper.xml

<select id="queryLang" resultType="Language">
   select id,
          code,
          name
   from LANG
</select>

如何在弹簧启动的mybatis中使用一对一映射？

2 个答案: