Mybatis基础支持层-反射模块：类型转换
一、codeLookUp
-
维护数据库类型和java类型之间的映射
-
java.sql.Types类，记录了数据库中的一些数据类型的code
public enum JdbcType {
/*
* This is added to enable basic support for the
* ARRAY data type - but a custom type handler is still required
*/
ARRAY(Types.ARRAY),
BIT(Types.BIT),
TINYINT(Types.TINYINT),
SMALLINT(Types.SMALLINT),
INTEGER(Types.INTEGER),
BIGINT(Types.BIGINT),
FLOAT(Types.FLOAT),
REAL(Types.REAL),
DOUBLE(Types.DOUBLE),
NUMERIC(Types.NUMERIC),
DECIMAL(Types.DECIMAL),
CHAR(Types.CHAR),
VARCHAR(Types.VARCHAR),
LONGVARCHAR(Types.LONGVARCHAR),
DATE(Types.DATE),
TIME(Types.TIME),
TIMESTAMP(Types.TIMESTAMP),
BINARY(Types.BINARY),
VARBINARY(Types.VARBINARY),
LONGVARBINARY(Types.LONGVARBINARY),
NULL(Types.NULL),
OTHER(Types.OTHER),
BLOB(Types.BLOB),
CLOB(Types.CLOB),
BOOLEAN(Types.BOOLEAN),
CURSOR(-10), // Oracle
UNDEFINED(Integer.MIN_VALUE + 1000),
NVARCHAR(Types.NVARCHAR), // JDK6
NCHAR(Types.NCHAR), // JDK6
NCLOB(Types.NCLOB), // JDK6
STRUCT(Types.STRUCT),
JAVA_OBJECT(Types.JAVA_OBJECT),
DISTINCT(Types.DISTINCT),
REF(Types.REF),
DATALINK(Types.DATALINK),
ROWID(Types.ROWID), // JDK6
LONGNVARCHAR(Types.LONGNVARCHAR), // JDK6
SQLXML(Types.SQLXML), // JDK6
DATETIMEOFFSET(-155), // SQL Server 2008
TIME_WITH_TIMEZONE(Types.TIME_WITH_TIMEZONE), // JDBC 4.2 JDK8
TIMESTAMP_WITH_TIMEZONE(Types.TIMESTAMP_WITH_TIMEZONE); // JDBC 4.2 JDK8
public final int TYPE_CODE;
private static Map<Integer,JdbcType> codeLookup = new HashMap<>();
static {
for (JdbcType type : JdbcType.values()) {
codeLookup.put(type.TYPE_CODE, type);
}
}
JdbcType(int code) {
this.TYPE_CODE = code;
}
public static JdbcType forCode(int code) {
return codeLookup.get(code);
}
}
二、TypeHandler
主要解决prepare statement中的参数java与jdbc类型转换，以及result中java类型与jdbc类型的转换
public interface TypeHandler<T> {
//通过prepareStatement 为SQL绑定参数，将JdbcType转换为java类型
void setParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException;
/**
* Gets the result.
* 获取数据时，将java类型转换为jdbcType
*
* @param rs
* the rs
* @param columnName
* Colunm name, when configuration <code>useColumnLabel</code> is <code>false</code>
* @return the result
* @throws SQLException
* the SQL exception
*/
T getResult(ResultSet rs, String columnName) throws SQLException;
T getResult(ResultSet rs, int columnIndex) throws SQLException;
T getResult(CallableStatement cs, int columnIndex) throws SQLException;
}
TypeHandler
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BaseTypeHandler
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IntegerTypeHandler........
public class IntegerTypeHandler extends BaseTypeHandler<Integer> {
@Override
public void setNonNullParameter(PreparedStatement ps, int i, Integer parameter, JdbcType jdbcType)
throws SQLException {
//通过PreparedStatement 进行参数的设置
ps.setInt(i, parameter);
}
@Override
public Integer getNullableResult(ResultSet rs, String columnName)
throws SQLException {
//ResultSet中获取值
int result = rs.getInt(columnName);
return result == 0 && rs.wasNull() ? null : result;
}
...
}
三、TypeHandlerRegister
注册各类型对应jdbc类型以及handler的绑定关系，存在一对多的关系（string类型为例）
1. 含有的内部变量
//jdbc类型处理器Map,用于从resultSet中读取参数映射到JAVA类型上
private final Map<JdbcType, TypeHandler<?>> jdbcTypeHandlerMap = new EnumMap<>(JdbcType.class);
//java 类型和jdbc类型与映射器Map
private final Map<Type, Map<JdbcType, TypeHandler<?>>> typeHandlerMap = new ConcurrentHashMap<>();
private final TypeHandler<Object> unknownTypeHandler;
//typeHandler类型和对应处理器的映射
private final Map<Class<?>, TypeHandler<?>> allTypeHandlersMap = new HashMap<>();
//NULL_TYPE_HANDLER_MAP
private static final Map<JdbcType, TypeHandler<?>> NULL_TYPE_HANDLER_MAP = Collections.emptyMap();
private Class<? extends TypeHandler> defaultEnumTypeHandler = EnumTypeHandler.class;
2. 通过register构造方法，注册类型处理器
public TypeHandlerRegistry(Configuration configuration) {
this.unknownTypeHandler = new UnknownTypeHandler(configuration);
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 StringTypeHandler());
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 StringTypeHandler());
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, unknownTypeHandler);
register(Object.class, JdbcType.OTHER, unknownTypeHandler);
register(JdbcType.OTHER, unknownTypeHandler);
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());
register(String.class, JdbcType.SQLXML, new SqlxmlTypeHandler());
register(Instant.class, new InstantTypeHandler());
register(LocalDateTime.class, new LocalDateTimeTypeHandler());
register(LocalDate.class, new LocalDateTypeHandler());
register(LocalTime.class, new LocalTimeTypeHandler());
register(OffsetDateTime.class, new OffsetDateTimeTypeHandler());
register(OffsetTime.class, new OffsetTimeTypeHandler());
register(ZonedDateTime.class, new ZonedDateTimeTypeHandler());
register(Month.class, new MonthTypeHandler());
register(Year.class, new YearTypeHandler());
register(YearMonth.class, new YearMonthTypeHandler());
register(JapaneseDate.class, new JapaneseDateTypeHandler());
// issue #273
register(Character.class, new CharacterTypeHandler());
register(char.class, new CharacterTypeHandler());
}
3. 实现注册的register方法
- 通过可以接受java类型、jdbc类型、处理器三部分参数，实现注册
//最终调用的方法，包含Java类型、jdbc类型、处理器
private void register(Type javaType, JdbcType jdbcType, TypeHandler<?> handler) {
if (javaType != null) {
Map<JdbcType, TypeHandler<?>> map = typeHandlerMap.get(javaType);
if (map == null || map == NULL_TYPE_HANDLER_MAP) {
map = new HashMap<>();
}
map.put(jdbcType, handler);
typeHandlerMap.put(javaType, map);
}
allTypeHandlersMap.put(handler.getClass(), handler);
}
//对应处理器绑定的MappedTypes注解，确定java类型
public <T> void register(TypeHandler<T> typeHandler);
//找到handler对应的MappedJdbcTypes注解，获取对应jdbc类型
public <T> void register(Class<T> javaType, TypeHandler<? extends T> typeHandler);
//对应处理器绑定的MappedTypes注解，确定java类型
public void register(Class<?> typeHandlerClass);
//传入java类型名称、处理器对象名称，查找对应的java类型和typehandler
public void register(String javaTypeClassName, String typeHandlerClassName) throws ClassNotFoundException;
//传入java类型类、处理器对象类，查找对应的java类型和typehandler
public void register(Class<?> javaTypeClass, Class<?> typeHandlerClass);
// java type + jdbc type + handler type
public void register(Class<?> javaTypeClass, JdbcType jdbcType, Class<?> typeHandlerClass);
//扫描包，自动注入包中的handler
public void register(String packageName) ;
4. 获取TypeHandler
public Collection<TypeHandler<?>> getTypeHandlers() {
//根据allTypeHandlersMap绑定的处理器页表，此处返回的集合是不可修改的
return Collections.unmodifiableCollection(allTypeHandlersMap.values());
}
@SuppressWarnings("unchecked")
private <T> TypeHandler<T> getTypeHandler(Type type, JdbcType jdbcType) {
if (ParamMap.class.equals(type)) {
return null;
}
Map<JdbcType, TypeHandler<?>> jdbcHandlerMap = getJdbcHandlerMap(type);
TypeHandler<?> handler = null;
if (jdbcHandlerMap != null) {
//查找java类型对应处理器
handler = jdbcHandlerMap.get(jdbcType);
if (handler == null) {
handler = jdbcHandlerMap.get(null);
}
if (handler == null) {
// #591如果只注册了一个handler
handler = pickSoleHandler(jdbcHandlerMap);
}
}
// type drives generics here
return (TypeHandler<T>) handler;
}
四、TypeAliasRegistry
- 属性
//别名字段与类型做绑定
private final Map<String, Class<?>> typeAliases = new HashMap<>();
- 构造函，进行绑定参数的注入
public TypeAliasRegistry() {
registerAlias("string", String.class);
registerAlias("byte", Byte.class);
registerAlias("long", Long.class);
registerAlias("short", Short.class);
registerAlias("int", Integer.class);
registerAlias("integer", Integer.class);
registerAlias("double", Double.class);
registerAlias("float", Float.class);
registerAlias("boolean", Boolean.class);
registerAlias("byte[]", Byte[].class);
registerAlias("long[]", Long[].class);
registerAlias("short[]", Short[].class);
registerAlias("int[]", Integer[].class);
registerAlias("integer[]", Integer[].class);
registerAlias("double[]", Double[].class);
registerAlias("float[]", Float[].class);
registerAlias("boolean[]", Boolean[].class);
registerAlias("_byte", byte.class);
registerAlias("_long", long.class);
registerAlias("_short", short.class);
registerAlias("_int", int.class);
registerAlias("_integer", int.class);
registerAlias("_double", double.class);
registerAlias("_float", float.class);
registerAlias("_boolean", boolean.class);
registerAlias("_byte[]", byte[].class);
registerAlias("_long[]", long[].class);
registerAlias("_short[]", short[].class);
registerAlias("_int[]", int[].class);
registerAlias("_integer[]", int[].class);
registerAlias("_double[]", double[].class);
registerAlias("_float[]", float[].class);
registerAlias("_boolean[]", boolean[].class);
registerAlias("date", Date.class);
registerAlias("decimal", BigDecimal.class);
registerAlias("bigdecimal", BigDecimal.class);
registerAlias("biginteger", BigInteger.class);
registerAlias("object", Object.class);
registerAlias("date[]", Date[].class);
registerAlias("decimal[]", BigDecimal[].class);
registerAlias("bigdecimal[]", BigDecimal[].class);
registerAlias("biginteger[]", BigInteger[].class);
registerAlias("object[]", Object[].class);
registerAlias("map", Map.class);
registerAlias("hashmap", HashMap.class);
registerAlias("list", List.class);
registerAlias("arraylist", ArrayList.class);
registerAlias("collection", Collection.class);
registerAlias("iterator", Iterator.class);
registerAlias("ResultSet", ResultSet.class);
}
//放入map的步骤非常简单
public void registerAlias(String alias, Class<?> value) {
if (alias == null) {
throw new TypeException("The parameter alias cannot be null");
}
// issue #748
//转换key
String key = alias.toLowerCase(Locale.ENGLISH);
if (typeAliases.containsKey(key) && typeAliases.get(key) != null && !typeAliases.get(key).equals(value)) {
//已存在指定别名，不允许不同的别名
throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + typeAliases.get(key).getName() + "'.");
}
typeAliases.put(key, value);
}
//扫描包，未指定类子类添加别名
public void registerAliases(String packageName) {
registerAliases(packageName, Object.class);
}
public void registerAliases(String packageName, Class<?> superType) {
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<>();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
Set<Class<? extends Class<?>>> typeSet = resolverUtil.getClasses();
for (Class<?> type : typeSet) {
// Ignore inner classes and interfaces (including package-info.java)
// Skip also inner classes. See issue #6
if (!type.isAnonymousClass() && !type.isInterface() && !type.isMemberClass()) {
registerAlias(type);
}
}
}
public void registerAlias(Class<?> type) {
String alias = type.getSimpleName();
//读取alias注解
Alias aliasAnnotation = type.getAnnotation(Alias.class);
if (aliasAnnotation != null) {
alias = aliasAnnotation.value();
}
registerAlias(alias, type);
}
