Mybatis的数据库字段类型JDBCType和java基本数据类型转换说明

太过爱你忘了你带给我的痛 2022-09-30 06:30 340阅读 0赞

我们在设计数据库的时候，往往需要注意数据库字段的类型和java的基本数据类型的对应关系，以便合理设计java实体；其实Mybaits里数据库字段类型

和java数据类型的转换，都是由一个个typeHandler进行转换，如：BooleanTypeHandler、ShortTypeHandler、LongTypeHandler。。。而他们的基类都是

BaseTypeHandler，如果我们想自定义自己的类型转换器，也需要继承于该类；如下图是Mybatis默认给我们注册和实现的typeHandler

register(Boolean.class, new BooleanTypeHandler());  
    register(Boolean.TYPE, new BooleanTypeHandler());  
    register(JdbcType.BOOLEAN, new BooleanTypeHandler());  
    register(JdbcType.BIT, new BooleanTypeHandler());

register(Byte.class, new ByteTypeHandler());  
    register(Byte.TYPE, new ByteTypeHandler());  
    register(JdbcType.TINYINT, new ByteTypeHandler());

register(Short.class, new ShortTypeHandler());  
    register(Short.TYPE, new ShortTypeHandler());  
    register(JdbcType.SMALLINT, new ShortTypeHandler());

register(Integer.class, new IntegerTypeHandler());  
    register(Integer.TYPE, new IntegerTypeHandler());  
    register(JdbcType.INTEGER, new IntegerTypeHandler());

register(Float.class, new FloatTypeHandler());  
    register(Float.TYPE, new FloatTypeHandler());  
    register(JdbcType.FLOAT, new FloatTypeHandler());

register(Double.class, new DoubleTypeHandler());  
    register(Double.TYPE, new DoubleTypeHandler());  
    register(JdbcType.DOUBLE, new DoubleTypeHandler());

register(Reader.class, new ClobReaderTypeHandler());  
    register(String.class, new StringTypeHandler());  
    register(String.class, JdbcType.CHAR, new StringTypeHandler());  
    register(String.class, JdbcType.CLOB, new ClobTypeHandler());  
    register(String.class, JdbcType.VARCHAR, new StringTypeHandler());  
    register(String.class, JdbcType.LONGVARCHAR, new ClobTypeHandler());  
    register(String.class, JdbcType.NVARCHAR, new NStringTypeHandler());  
    register(String.class, JdbcType.NCHAR, new NStringTypeHandler());  
    register(String.class, JdbcType.NCLOB, new NClobTypeHandler());  
    register(JdbcType.CHAR, new StringTypeHandler());  
    register(JdbcType.VARCHAR, new StringTypeHandler());  
    register(JdbcType.CLOB, new ClobTypeHandler());  
    register(JdbcType.LONGVARCHAR, new ClobTypeHandler());  
    register(JdbcType.NVARCHAR, new NStringTypeHandler());  
    register(JdbcType.NCHAR, new NStringTypeHandler());  
    register(JdbcType.NCLOB, new NClobTypeHandler());

register(BigDecimal.class, new BigDecimalTypeHandler());  
    register(JdbcType.REAL, new BigDecimalTypeHandler());  
    register(JdbcType.DECIMAL, new BigDecimalTypeHandler());  
    register(JdbcType.NUMERIC, new BigDecimalTypeHandler());

register(InputStream.class, new BlobInputStreamTypeHandler());  
    register(\[Ljava.lang.Byte.class, new ByteObjectArrayTypeHandler());  
    register(\[Ljava.lang.Byte.class, JdbcType.BLOB, new BlobByteObjectArrayTypeHandler());  
    register(\[Ljava.lang.Byte.class, JdbcType.LONGVARBINARY, new BlobByteObjectArrayTypeHandler());  
    register(\[B.class, new ByteArrayTypeHandler());  
    register(\[B.class, JdbcType.BLOB, new BlobTypeHandler());  
    register(\[B.class, JdbcType.LONGVARBINARY, new BlobTypeHandler());  
    register(JdbcType.LONGVARBINARY, new BlobTypeHandler());  
    register(JdbcType.BLOB, new BlobTypeHandler());

register(Object.class, this.UNKNOWN\_TYPE\_HANDLER);  
    register(Object.class, JdbcType.OTHER, this.UNKNOWN\_TYPE\_HANDLER);  
    register(JdbcType.OTHER, this.UNKNOWN\_TYPE\_HANDLER);

register(java.util.Date.class, new DateTypeHandler());  
    register(java.util.Date.class, JdbcType.DATE, new DateOnlyTypeHandler());  
    register(java.util.Date.class, JdbcType.TIME, new TimeOnlyTypeHandler());  
    register(JdbcType.TIMESTAMP, new DateTypeHandler());  
    register(JdbcType.DATE, new DateOnlyTypeHandler());  
    register(JdbcType.TIME, new TimeOnlyTypeHandler());

register(java.sql.Date.class, new SqlDateTypeHandler());  
    register(Time.class, new SqlTimeTypeHandler());  
    register(Timestamp.class, new SqlTimestampTypeHandler());  
    try  
    \{  
      register("java.time.Instant", "org.apache.ibatis.type.InstantTypeHandler");  
      register("java.time.LocalDateTime", "org.apache.ibatis.type.LocalDateTimeTypeHandler");  
      register("java.time.LocalDate", "org.apache.ibatis.type.LocalDateTypeHandler");  
      register("java.time.LocalTime", "org.apache.ibatis.type.LocalTimeTypeHandler");  
      register("java.time.OffsetDateTime", "org.apache.ibatis.type.OffsetDateTimeTypeHandler");  
      register("java.time.OffsetTime", "org.apache.ibatis.type.OffsetTimeTypeHandler");  
      register("java.time.ZonedDateTime", "org.apache.ibatis.type.ZonedDateTimeTypeHandler");

register("java.time.Month", "org.apache.ibatis.type.MonthTypeHandler");  
      register("java.time.Year", "org.apache.ibatis.type.YearTypeHandler");

register("java.time.YearMonth", "org.apache.ibatis.type.YearMonthTypeHandler");  
      register("java.time.chrono.JapaneseDate", "org.apache.ibatis.type.JapaneseDateTypeHandler");  
    \}  
    catch (ClassNotFoundException localClassNotFoundException)  
    \{  
    \}

register(Character.class, new CharacterTypeHandler());  
    register(Character.TYPE, new CharacterTypeHandler());  
  \}

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