1.介绍：
建立TypeHandler来对特殊的javaType和jdbcType的转换
2.常用的类型转化：
1 register(Boolean.class, new BooleanTypeHandler()); 2 register(boolean.class, new BooleanTypeHandler()); 3 register(Byte.class, new ByteTypeHandler()); 4 register(byte.class, new ByteTypeHandler()); 5 register(Short.class, new ShortTypeHandler()); 6 register(short.class, new ShortTypeHandler()); 7 register(Integer.class, new IntegerTypeHandler()); 8 register(int.class, new IntegerTypeHandler()); 9 register(Long.class, new LongTypeHandler()); 10 register(long.class, new LongTypeHandler()); 11 register(Float.class, new FloatTypeHandler()); 12 register(float.class, new FloatTypeHandler()); 13 register(Double.class, new DoubleTypeHandler()); 14 register(double.class, new DoubleTypeHandler()); 15 register(String.class, new StringTypeHandler()); 16 register(String.class, JdbcType.CHAR, new StringTypeHandler()); 17 register(String.class, JdbcType.CLOB, new ClobTypeHandler()); 18 register(String.class, JdbcType.VARCHAR, new StringTypeHandler()); 19 register(String.class, JdbcType.LONGVARCHAR, new ClobTypeHandler()); 20 register(String.class, JdbcType.NVARCHAR, new NStringTypeHandler()); 21 register(String.class, JdbcType.NCHAR, new NStringTypeHandler()); 22 register(String.class, JdbcType.NCLOB, new NClobTypeHandler()); 23 register(Object.class, JdbcType.ARRAY, new ArrayTypeHandler()); 24 register(BigInteger.class, new BigIntegerTypeHandler()); 25 register(BigDecimal.class, new BigDecimalTypeHandler()); 26 register(Byte[].class, new ByteObjectArrayTypeHandler()); 27 register(Byte[].class, JdbcType.BLOB, new BlobByteObjectArrayTypeHandler()); 28 register(Byte[].class, JdbcType.LONGVARBINARY, new BlobByteObjectArrayTypeHandler()); 29 register(byte[].class, new ByteArrayTypeHandler()); 30 register(byte[].class, JdbcType.BLOB, new BlobTypeHandler()); 31 register(byte[].class, JdbcType.LONGVARBINARY, new BlobTypeHandler()); 32 register(Object.class, UNKNOWN_TYPE_HANDLER); 33 register(Object.class, JdbcType.OTHER, UNKNOWN_TYPE_HANDLER); 34 register(Date.class, new DateTypeHandler()); 35 register(Date.class, JdbcType.DATE, new DateOnlyTypeHandler()); 36 register(Date.class, JdbcType.TIME, new TimeOnlyTypeHandler()); 37 register(java.sql.Date.class, new SqlDateTypeHandler()); 38 register(java.sql.Time.class, new SqlTimeTypeHandler()); 39 register(java.sql.Timestamp.class, new SqlTimestampTypeHandler()); 40 register(Character.class, new CharacterTypeHandler()); 41 register(char.class, new CharacterTypeHandler());
3.实现
3.1 实现TypeHandler接口或者继承BaseTypeHandler抽象类
- BaseTypeHandler主要是在TypeHandler接口的基础上，对数据进行判空处理，并且继承了抽象类TypeReference。
- TypeReference可以通过getRawType()方法可以获取到当前TypeHandler所使用泛型的原始类型
3.2 简单介绍
TypeHandler<T>接口 ：
setParameter(PreparedStatement ps, int i, T parameter,JdbcType jdbcType)//实现对配置的javaType类型转换成jdbcType类型的处理
getResult(ResultSet rs, String columnName)//以下三种方式对应 jdbcType类型转换成javaType类型的处理
getResult(ResultSet rs, int columnIndex)
getResult(CallableStatement cs, int columnIndex)
BaseTypeHandler<T>抽象类：(推荐使用此种方式)
setNonNullParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType)//实现对配置的javaType类型转换成jdbcType类型的处理
getNullableResult(ResultSet rs, String columnName)//以下三种方式对应 jdbcType类型转换成javaType类型的处理
getNullableResult(ResultSet rs, int columnIndex)
getNullableResult(CallableStatement cs, int columnIndex)
3.3 配置方式
3.3.1 纯xml
<!-- mybatis.xml配置 -->
<typeHandlers>
<typeHandler handler="com.*.StringArrayTypeHandler" javaType="[Ljava.lang.String;" jdbcType="VARCHAR"/>
</typeHandlers>
3.3.2 注解与xml配置
<typeHandlers> <typeHandler handler="com.*.StringArrayTypeHandler"/> </typeHandlers> @MappedTypes({String[].class}) @MappedJdbcTypes({JdbcType.VARCHAR}) public class StringArrayTypeHandler implements BaseTypeHandler<String[]>
3.3.3 扫描包下的注解，实现类需要包含@MappedJdbcTypes和@MappedTypes
<typeHandlers>
<package name="com.*"/>
</typeHandlers>