/*
* Copyright 2009-2013 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ibatis.type;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import org.apache.ibatis.io.ResolverUtil;
import org.apache.ibatis.io.Resources;
/**
* @author Clinton Begin
*/
/**
* 类型别名注册机
*
*/
public class TypeAliasRegistry {
private final Map<String, Class<?>> TYPE_ALIASES = new HashMap<String, Class<?>>();
public TypeAliasRegistry() {
//构造函数里注册系统内置的类型别名
registerAlias("string", String.class);
//基本包装类型
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);
//基本数组包装类型
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);
//加个下划线，就变成了基本类型
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);
//加个下划线，就变成了基本数组类型
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);
//日期数字型
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);
//集合型
registerAlias("map", Map.class);
registerAlias("hashmap", HashMap.class);
registerAlias("list", List.class);
registerAlias("arraylist", ArrayList.class);
registerAlias("collection", Collection.class);
registerAlias("iterator", Iterator.class);
//还有个ResultSet型
registerAlias("ResultSet", ResultSet.class);
}
@SuppressWarnings("unchecked")
// throws class cast exception as well if types cannot be assigned
//解析类型别名
public <T> Class<T> resolveAlias(String string) {
try {
if (string == null) {
return null;
}
// issue #748
//先转成小写再解析
//这里转个小写也有bug？见748号bug(在google code上)
//https://code.google.com/p/mybatis/issues
//比如如果本地语言是Turkish，那i转成大写就不是I了，而是另外一个字符（İ）。这样土耳其的机器就用不了mybatis了！这是一个很大的bug，但是基本上每个人都会犯......
String key = string.toLowerCase(Locale.ENGLISH);
Class<T> value;
//原理就很简单了，从HashMap里找对应的键值，找到则返回类型别名对应的Class
if (TYPE_ALIASES.containsKey(key)) {
value = (Class<T>) TYPE_ALIASES.get(key);
} else {
//找不到，再试着将String直接转成Class(这样怪不得我们也可以直接用java.lang.Integer的方式定义，也可以就int这么定义)
value = (Class<T>) Resources.classForName(string);
}
return value;
} catch (ClassNotFoundException e) {
throw new TypeException("Could not resolve type alias '" + string + "'. Cause: " + e, e);
}
}
public void registerAliases(String packageName){
registerAliases(packageName, Object.class);
}
//扫描并注册包下所有继承于superType的类型别名
public void registerAliases(String packageName, Class<?> superType){
//TODO ResolverUtil
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
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);
}
}
}
//注册类型别名
public void registerAlias(Class<?> type) {
//如果没有类型别名，用Class.getSimpleName来注册
String alias = type.getSimpleName();
//或者通过Alias注解来注册(Class.getAnnotation)
Alias aliasAnnotation = type.getAnnotation(Alias.class);
if (aliasAnnotation != null) {
alias = aliasAnnotation.value();
}
registerAlias(alias, type);
}
//注册类型别名
public void registerAlias(String alias, Class<?> value) {
if (alias == null) {
throw new TypeException("The parameter alias cannot be null");
}
// issue #748
String key = alias.toLowerCase(Locale.ENGLISH);
//如果已经存在key了，且value和之前不一致，报错
//这里逻辑略显复杂，感觉没必要，一个key对一个value呗，存在key直接报错不就得了
if (TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key) != null && !TYPE_ALIASES.get(key).equals(value)) {
throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + TYPE_ALIASES.get(key).getName() + "'.");
}
TYPE_ALIASES.put(key, value);
}
public void registerAlias(String alias, String value) {
try {
registerAlias(alias, Resources.classForName(value));
} catch (ClassNotFoundException e) {
throw new TypeException("Error registering type alias "+alias+" for "+value+". Cause: " + e, e);
}
}
/**
* @since 3.2.2
*/
public Map<String, Class<?>> getTypeAliases() {
return Collections.unmodifiableMap(TYPE_ALIASES);
}
}