一、首先分析AliasRegistry接口。
1、Alias别名，Registry注册表，AliasRegistry别名注册表接口。
2、共有四个方法，注册别名，判断是否别名，获取别名数组，移除别名。
3、我自己试着写了一个这个接口的实现类：
package com.lzh.spring.test; import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import org.springframework.core.AliasRegistry; /**
* 别名注册表接口的实现
* @author LiaoZhengHan
* @date 2018年8月29日
*/
public class MyAliasRegistry implements AliasRegistry{ private Map<String, String> aliasMap = new Hashtable<>(); @Override
public void registerAlias(String name, String alias) { if (isAlias(alias)) {
throw new IllegalStateException();
} aliasMap.put(alias, name);
} @Override
public void removeAlias(String alias) {
aliasMap.remove(alias);
} @Override
public boolean isAlias(String name) {
return aliasMap.containsKey(name);
} @Override
public String[] getAliases(String name) { List<String> aliases = new ArrayList<>();
Iterator<Entry<String, String>> it = aliasMap.entrySet().iterator();
Entry<String, String> entry = null;
while (it.hasNext()) {
entry = it.next();
if (entry.getValue().equals(name)) {
aliases.add(entry.getKey());
}
}
String[] array = new String[aliases.size()];
return aliases.toArray(array);
} }
/*
* Copyright 2002-2012 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.springframework.core; import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap; import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.util.StringValueResolver; /**
* Simple implementation of the {@link AliasRegistry} interface.
* Serves as base class for
* {@link org.springframework.beans.factory.support.BeanDefinitionRegistry}
* implementations.
*
* @author Juergen Hoeller
* @since 2.5.2
*/
public class SimpleAliasRegistry implements AliasRegistry { /** Map from alias to canonical name */
private final Map<String, String> aliasMap = new ConcurrentHashMap<String, String>(16); @Override
public void registerAlias(String name, String alias) {
Assert.hasText(name, "'name' must not be empty");
Assert.hasText(alias, "'alias' must not be empty");
if (alias.equals(name)) {
this.aliasMap.remove(alias);
}
else {
if (!allowAliasOverriding()) {
String registeredName = this.aliasMap.get(alias);
if (registeredName != null && !registeredName.equals(name)) {
throw new IllegalStateException("Cannot register alias '" + alias + "' for name '" +
name + "': It is already registered for name '" + registeredName + "'.");
}
}
checkForAliasCircle(name, alias);
this.aliasMap.put(alias, name);
}
} /**
* Return whether alias overriding is allowed.
* Default is {@code true}.
*/
protected boolean allowAliasOverriding() {
return true;
} @Override
public void removeAlias(String alias) {
String name = this.aliasMap.remove(alias);
if (name == null) {
throw new IllegalStateException("No alias '" + alias + "' registered");
}
} @Override
public boolean isAlias(String name) {
return this.aliasMap.containsKey(name);
} @Override
public String[] getAliases(String name) {
List<String> result = new ArrayList<String>();
synchronized (this.aliasMap) {
retrieveAliases(name, result);
}
return StringUtils.toStringArray(result);
} /**
* Transitively retrieve all aliases for the given name.
* @param name the target name to find aliases for
* @param result the resulting aliases list
*/
private void retrieveAliases(String name, List<String> result) {
for (Map.Entry<String, String> entry : this.aliasMap.entrySet()) {
String registeredName = entry.getValue();
if (registeredName.equals(name)) {
String alias = entry.getKey();
result.add(alias);
retrieveAliases(alias, result);
}
}
} /**
* Resolve all alias target names and aliases registered in this
* factory, applying the given StringValueResolver to them.
* <p>The value resolver may for example resolve placeholders
* in target bean names and even in alias names.
* @param valueResolver the StringValueResolver to apply
*/
public void resolveAliases(StringValueResolver valueResolver) {
Assert.notNull(valueResolver, "StringValueResolver must not be null");
synchronized (this.aliasMap) {
Map<String, String> aliasCopy = new HashMap<String, String>(this.aliasMap);
for (String alias : aliasCopy.keySet()) {
String registeredName = aliasCopy.get(alias);
String resolvedAlias = valueResolver.resolveStringValue(alias);
String resolvedName = valueResolver.resolveStringValue(registeredName);
if (resolvedAlias.equals(resolvedName)) {
this.aliasMap.remove(alias);
}
else if (!resolvedAlias.equals(alias)) {
String existingName = this.aliasMap.get(resolvedAlias);
if (existingName != null && !existingName.equals(resolvedName)) {
throw new IllegalStateException(
"Cannot register resolved alias '" + resolvedAlias + "' (original: '" + alias +
"') for name '" + resolvedName + "': It is already registered for name '" +
registeredName + "'.");
}
checkForAliasCircle(resolvedName, resolvedAlias);
this.aliasMap.remove(alias);
this.aliasMap.put(resolvedAlias, resolvedName);
}
else if (!registeredName.equals(resolvedName)) {
this.aliasMap.put(alias, resolvedName);
}
}
}
} /**
* Determine the raw name, resolving aliases to canonical names.
* @param name the user-specified name
* @return the transformed name
*/
public String canonicalName(String name) {
String canonicalName = name;
// Handle aliasing...
String resolvedName;
do {
resolvedName = this.aliasMap.get(canonicalName);
if (resolvedName != null) {
canonicalName = resolvedName;
}
}
while (resolvedName != null);
return canonicalName;
} /**
* Check whether the given name points back to given alias as an alias
* in the other direction, catching a circular reference upfront and
* throwing a corresponding IllegalStateException.
* @param name the candidate name
* @param alias the candidate alias
* @see #registerAlias
*/
protected void checkForAliasCircle(String name, String alias) {
if (alias.equals(canonicalName(name))) {
throw new IllegalStateException("Cannot register alias '" + alias +
"' for name '" + name + "': Circular reference - '" +
name + "' is a direct or indirect alias for '" + alias + "' already");
}
} }