回顾
上一次我们分析了TypeHandler的源码，了解了Mybatis内部的类型处理器的实现，本篇就来简要分析一下如何去注册TypeHandler。
类型处理器注册器
类型处理器注册器既能完成类型处理器的注册功能，同时也能对类型处理器进行统筹管理，其内部定义了集合来进行类型处理器的存取，同时定义了存取方法。
【TypeHandlerRegistry内部静态变量】
//枚举类JdbcType作为键，完成数据库类型与类型处理器的对应注册
private final Map> JDBC_TYPE_HANDLER_MAP = new EnumMap>(JdbcType.class);
//Java类型作为键，JdbcType与TypeHandler的映射关系作为value，完成Java类型、数据库类型和类型处理器三者的对应注册
private final Map>> TYPE_HANDLER_MAP = new HashMap>>();
//对未知类型的注册，如Object
private final TypeHandler 【基础类型处理器的对内注册】
- 对内注册是指Mybatis对内置的TypeHandler的注册过程
- 基础类型处理器的注册完成在TypeHandlerRegistry的构造函数中
public TypeHandlerRegistry() {
register(Boolean.class, new BooleanTypeHandler());
register(boolean.class, new BooleanTypeHandler());
register(JdbcType.BOOLEAN, new BooleanTypeHandler());
register(JdbcType.BIT, new BooleanTypeHandler());
register(Byte.class, new ByteTypeHandler());
register(byte.class, new ByteTypeHandler());
register(JdbcType.TINYINT, new ByteTypeHandler());
register(Short.class, new ShortTypeHandler());
register(short.class, new ShortTypeHandler());
register(JdbcType.SMALLINT, new ShortTypeHandler());
register(Integer.class, new IntegerTypeHandler());
register(int.class, new IntegerTypeHandler());
register(JdbcType.INTEGER, new IntegerTypeHandler());
register(Long.class, new LongTypeHandler());
register(long.class, new LongTypeHandler());
register(Float.class, new FloatTypeHandler());
register(float.class, new FloatTypeHandler());
register(JdbcType.FLOAT, new FloatTypeHandler());
register(Double.class, new DoubleTypeHandler());
register(double.class, 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(Object.class, JdbcType.ARRAY, new ArrayTypeHandler());
register(JdbcType.ARRAY, new ArrayTypeHandler());
register(BigInteger.class, new BigIntegerTypeHandler());
register(JdbcType.BIGINT, new LongTypeHandler());
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(Byte[].class, new ByteObjectArrayTypeHandler());
register(Byte[].class, JdbcType.BLOB, new BlobByteObjectArrayTypeHandler());
register(Byte[].class, JdbcType.LONGVARBINARY, new BlobByteObjectArrayTypeHandler());
register(byte[].class, new ByteArrayTypeHandler());
register(byte[].class, JdbcType.BLOB, new BlobTypeHandler());
register(byte[].class, JdbcType.LONGVARBINARY, new BlobTypeHandler());
register(JdbcType.LONGVARBINARY, new BlobTypeHandler());
register(JdbcType.BLOB, new BlobTypeHandler());
register(Object.class, UNKNOWN_TYPE_HANDLER);
register(Object.class, JdbcType.OTHER, UNKNOWN_TYPE_HANDLER);
register(JdbcType.OTHER, UNKNOWN_TYPE_HANDLER);
register(Date.class, new DateTypeHandler());
register(Date.class, JdbcType.DATE, new DateOnlyTypeHandler());
register(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(java.sql.Time.class, new SqlTimeTypeHandler());
register(java.sql.Timestamp.class, new SqlTimestampTypeHandler());
// mybatis-typehandlers-jsr310
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");
} catch (ClassNotFoundException e) {
// no JSR-310 handlers
}
// issue #273
register(Character.class, new CharacterTypeHandler());
register(char.class, new CharacterTypeHandler());
}
TypeHandlerRegistry提供了多种注册方法，各种注册方法之间也存在着一些调用，现以Integer为例简要分析。
register(Integer.class, new IntegerTypeHandler());//1
register(int.class, new IntegerTypeHandler());//与1相同
register(JdbcType.INTEGER, new IntegerTypeHandler());//2
【1】
// java type + handler（两者联合注册）
public void register(Class javaType, TypeHandler typeHandler) {
register((Type) javaType, typeHandler);
}
private void register(Type javaType, TypeHandler typeHandler) {
MappedJdbcTypes mappedJdbcTypes = typeHandler.getClass().getAnnotation(MappedJdbcTypes.class);
if (mappedJdbcTypes != null) {
for (JdbcType handledJdbcType : mappedJdbcTypes.value()) {
register(javaType, handledJdbcType, typeHandler);
}
if (mappedJdbcTypes.includeNullJdbcType()) {
register(javaType, null, typeHandler);
}
} else {
register(javaType, null, typeHandler);
}
}
- 在对Integer和int与IntegerTypeHandler注册时，采用java type + handler的形式，注册时首先判断TypeHandler是否有MappedJdbcTypes注解指明jdbc类型
- 有则使用java type + jdbc type + handler模式进行三者联合注册
- 没有则将jdbcType置为null然后进行三者联合注册
// java type + jdbc type + handler（三者联合注册）
// 一般所有的注册方法都会指向本方法
public void register(Class type, JdbcType jdbcType, TypeHandler handler) {
register((Type) type, jdbcType, handler);
}
private void register(Type javaType, JdbcType jdbcType, TypeHandler handler) {
if (javaType != null) {
Map> map = TYPE_HANDLER_MAP.get(javaType);
if (map == null) {
map = new HashMap>();
TYPE_HANDLER_MAP.put(javaType, map);
}
map.put(jdbcType, handler);
}
ALL_TYPE_HANDLERS_MAP.put(handler.getClass(), handler);
}
- javaType不为空时，从TYPE_HANDLER_MAP找出其对应的【JdbcType和TypeHandler】的映射关系，如果关系不存在，则新建一个映射关系。
- 将这种关系添加到TYPE_HANDLER_MAP中
- 将jdbcType与handler加到该映射关系中
- 完成JavaType、JdbcType和TypeHandler三者的注册
【2】
public void register(JdbcType jdbcType, TypeHandler handler) {
JDBC_TYPE_HANDLER_MAP.put(jdbcType, handler);
}
将JdbcType与TypeHandler映射关系添加到JDBC_TYPE_HANDLER_MAP中
【基础类型处理器的对外注册】
- Mybatis不仅内置了很多基础的类型处理器，也允许使用者根据需求自定义TypeHandler
- 为了方便使用者去注册自定义TypeHandler，Mybatis提供了很多注册方法，用户只需要提供自定义处理器的类路径
【Only handler type】
public void register(Class typeHandlerClass) {
boolean mappedTypeFound = false;
MappedTypes mappedTypes = typeHandlerClass.getAnnotation(MappedTypes.class);
if (mappedTypes != null) {
for (Class javaTypeClass : mappedTypes.value()) {
register(javaTypeClass, typeHandlerClass);
mappedTypeFound = true;
}
}
if (!mappedTypeFound) {
register(getInstance(null, typeHandlerClass));
}
}
【java type + handler type】
public void register(String javaTypeClassName, String typeHandlerClassName) throws ClassNotFoundException {
register(Resources.classForName(javaTypeClassName), Resources.classForName(typeHandlerClassName));
}
public void register(Class javaTypeClass, Class typeHandlerClass) {
register(javaTypeClass, getInstance(javaTypeClass, typeHandlerClass));
}
【java type + jdbc type + handler type】
public void register(Class javaTypeClass, JdbcType jdbcType, Class typeHandlerClass) {
register(javaTypeClass, jdbcType, getInstance(javaTypeClass, typeHandlerClass));
}
【scan package】
public void register(String packageName) {
ResolverUtil> resolverUtil = new ResolverUtil>();
resolverUtil.find(new ResolverUtil.IsA(TypeHandler.class), packageName);
Set>> handlerSet = resolverUtil.getClasses();
for (Class type : handlerSet) {
//Ignore inner classes and interfaces (including package-info.java) and abstract classes
if (!type.isAnonymousClass() && !type.isInterface() && !Modifier.isAbstract(type.getModifiers())) {
register(type);
}
}
}
用户只需要使用
//这样无法指定jdbcType和javaType，可以在自定义TypeHandler上使用注解去指定
//例如：@MappedTypes(String.class) @MappedjdbcTypes(jdbcType.VARCHAR)
或者
即可，Mybatis会自动的找到对应的注册方法去注册，一般注册最后都会指到上一小节所提到的【java type + jdbc type + handler（三者联合注册）】方法，它是核心方法。