typeAliases節點主要用來設置別名,其實這是挺好用的一個功能, 通過配置別名,我們不用再指定完整的包名,並且還能取別名。
可以通過別名和反射知識創建別名對應類型的實例
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;
public class TypeAliasRegistry {
//Class<?>它是個通配泛型,?可以代表任何類型
private final Map<String, Class<?>> TYPE_ALIASES = new HashMap<String, Class<?>>();
/**
* 默認爲通用類別取別名並註冊到map裏
*/
public TypeAliasRegistry() {
// TODO Auto-generated constructor stub
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);
}
/**
* 這個方法最重要 是講如何講將別名對應的類型註冊到map裏
* 將別名和別名對應的類型註冊到map裏
* @param alias 別名 爲key
* @param value 類型 爲value
*/
public void registerAlias(String alias , Class<?> value){
if(alias == null){
throw new TypeException("this parameter alias cannot be null");
}
String key = alias.toLowerCase(Locale.ENGLISH);
if((TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key)!=null) && ((Class)TYPE_ALIASES.get(key)).equals(value)){
throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + ((Class)TYPE_ALIASES.get(key)).getName() + "'.");
}
TYPE_ALIASES.put(key, value);
}
/**
* 獲取 TYPE_ALIASES
* @return
*/
public Map<String, Class<?>> getTypeAliases(){
return Collections.unmodifiableMap(TYPE_ALIASES);
}
}