Spring-SimpleAliasRegistry.md

Spring-SimpleAliasRegistry

• Author: HuiFer
• 源码阅读仓库: huifer-spring

AliasRegistry

• SimpleAliasRegistry继承org.springframework.core.AliasRegistry

publicinterfaceAliasRegistry { /** * Given a name, register an alias for it. * 别名注册 * * @param name the canonical name * @param alias the alias to be registered * @throws IllegalStateException if the alias is already in use * and may not be overridden * @see SimpleAliasRegistry * @see org.springframework.context.support.GenericApplicationContext */voidregisterAlias(Stringname, Stringalias); /** * Remove the specified alias from this registry. * 别名移除 * * @param alias the alias to remove * @throws IllegalStateException if no such alias was found */voidremoveAlias(Stringalias); /** * Determine whether this given name is defines as an alias * (as opposed to the name of an actually registered component). * 是不是别名 * * @param name the name to check * @return whether the given name is an alias */booleanisAlias(Stringname); /** * Return the aliases for the given name, if defined. * 从别名注册map中获取别名信息 * * @param name the name to check for aliases * @return the aliases, or an empty array if none */String[] getAliases(Stringname); }

SimpleAliasRegistry

/** * 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 */publicclassSimpleAliasRegistryimplementsAliasRegistry { /** * Logger available to subclasses. */protectedfinalLoglogger = LogFactory.getLog(getClass()); /** * Map from alias to canonical name. * 存放别名的map(线程安全的), * 结构: alias-> name */privatefinalMap<String, String> aliasMap = newConcurrentHashMap<>(16); /** * {@code <alias name="appleBean" alias="hhh"/>} * * @param name the canonical name * alias 标签的name属性 * @param alias the alias to be registered * alias 标签的alias属性 */@OverridepublicvoidregisterAlias(Stringname, Stringalias) { Assert.hasText(name, "'name' must not be empty"); Assert.hasText(alias, "'alias' must not be empty"); synchronized (this.aliasMap) { // 判断: 别名和名字是否相同if (alias.equals(name)) { //相同在别名map中移除this.aliasMap.remove(alias); if (logger.isDebugEnabled()) { logger.debug("Alias definition '" + alias + "' ignored since it points to same name"); } } else { // 不相同// 从map对象中获取别名为alias的valueStringregisteredName = this.aliasMap.get(alias); if (registeredName != null) { // 判断map中是否有有一个别名和传入的name相同的内容if (registeredName.equals(name)) { // An existing alias - no need to re-registerreturn; } if (!allowAliasOverriding()) { thrownewIllegalStateException("Cannot define alias '" + alias + "' for name '" + name + "': It is already registered for name '" + registeredName + "'."); } if (logger.isDebugEnabled()) { logger.debug("Overriding alias '" + alias + "' definition for registered name '" + registeredName + "' with new target name '" + name + "'"); } } // 别名环检查checkForAliasCircle(name, alias); // 放入 map 对象中 alias-> namethis.aliasMap.put(alias, name); if (logger.isTraceEnabled()) { logger.trace("Alias definition '" + alias + "' registered for name '" + name + "'"); } } } } /** * Return whether alias overriding is allowed. * Default is {@code true}. * 是否允许重写别名 */protectedbooleanallowAliasOverriding() { returntrue; } /** * Determine whether the given name has the given alias registered. * <p> * 递归判断是否已经存在别名 * * @param name the name to check * @param alias the alias to look for * @since 4.2.1 */publicbooleanhasAlias(Stringname, Stringalias) { for (Map.Entry<String, String> entry : this.aliasMap.entrySet()) { // 获取key值StringregisteredName = entry.getValue(); if (registeredName.equals(name)) { StringregisteredAlias = entry.getKey(); // 循环引用判断if (registeredAlias.equals(alias) || hasAlias(registeredAlias, alias)) { returntrue; } } } returnfalse; } /** * 别名移除 * * @param alias the alias to remove */@OverridepublicvoidremoveAlias(Stringalias) { synchronized (this.aliasMap) { // 判断是否移除成功Stringname = this.aliasMap.remove(alias); if (name == null) { thrownewIllegalStateException("No alias '" + alias + "' registered"); } } } /** * 判断是否是一个别名,校验方式{@link org.springframework.core.SimpleAliasRegistry#aliasMap} 的key是否包含 * * @param name the name to check * @return */@OverridepublicbooleanisAlias(Stringname) { returnthis.aliasMap.containsKey(name); } /** * 获取别名列表 * * @param name the name to check for aliases * @return */@OverridepublicString[] getAliases(Stringname) { List<String> result = newArrayList<>(); synchronized (this.aliasMap) { retrieveAliases(name, result); } returnStringUtils.toStringArray(result); } /** * Transitively retrieve all aliases for the given name. * 根据 name 获取别名 * * @param name the target name to find aliases for * @param result the resulting aliases list */privatevoidretrieveAliases(Stringname, List<String> result) { // 循环获取this.aliasMap.forEach((alias, registeredName) -> { if (registeredName.equals(name)) { result.add(alias); // 递归查询循环引用的别名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 */publicvoidresolveAliases(StringValueResolvervalueResolver) { Assert.notNull(valueResolver, "StringValueResolver must not be null"); synchronized (this.aliasMap) { Map<String, String> aliasCopy = newHashMap<>(this.aliasMap); aliasCopy.forEach((alias, registeredName) -> { StringresolvedAlias = valueResolver.resolveStringValue(alias); StringresolvedName = valueResolver.resolveStringValue(registeredName); if (resolvedAlias == null || resolvedName == null || resolvedAlias.equals(resolvedName)) { this.aliasMap.remove(alias); } elseif (!resolvedAlias.equals(alias)) { StringexistingName = this.aliasMap.get(resolvedAlias); if (existingName != null) { if (existingName.equals(resolvedName)) { // Pointing to existing alias - just remove placeholderthis.aliasMap.remove(alias); return; } thrownewIllegalStateException( "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); } elseif (!registeredName.equals(resolvedName)) { this.aliasMap.put(alias, resolvedName); } }); } } /** * Check whether the given name points back to the given alias as an alias * in the other direction already, catching a circular reference upfront * and throwing a corresponding IllegalStateException. * <p> * 判断是否循环别名 * * @param name the candidate name * @param alias the candidate alias * @see #registerAlias * @see #hasAlias */protectedvoidcheckForAliasCircle(Stringname, Stringalias) { if (hasAlias(alias, name)) { thrownewIllegalStateException("Cannot register alias '" + alias + "' for name '" + name + "': Circular reference - '" + name + "' is a direct or indirect alias for '" + alias + "' already"); } } /** * Determine the raw name, resolving aliases to canonical names. * * @param name the user-specified name * @return the transformed name */publicStringcanonicalName(Stringname) { StringcanonicalName = name; // Handle aliasing...StringresolvedName; do { resolvedName = this.aliasMap.get(canonicalName); if (resolvedName != null) { canonicalName = resolvedName; } } while (resolvedName != null); returncanonicalName; } }