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网上学电脑培训中心,关键词如何优化排名,用本机做网站浏览,网站建设1引言 determineCandidateConstructors——spring创建实例无法避免的一个方法，大家一起学习，让我们对spring创建bean的过程更加深刻代码 Nullablepublic Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, final Str…

引言

determineCandidateConstructors——spring创建实例无法避免的一个方法，大家一起学习，让我们对spring创建bean的过程更加深刻

代码

    @Nullablepublic Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, final String beanName) throws BeanCreationException {
//在开始处理构造函数之前，先检查beanClass中是否存在@Lookup注解的方法。如果有，可能会影响构造函数的选择。this.checkLookupMethods(beanClass, beanName);
//首先尝试从缓存candidateConstructorsCache中获取该beanClass的候选构造函数。
//如果缓存中不存在，则进入同步块进一步处理。Constructor<?>[] candidateConstructors = (Constructor[])this.candidateConstructorsCache.get(beanClass);if (candidateConstructors == null) {
//使用同步块确保线程安全，避免多个线程同时处理同一个beanClass的构造函数。synchronized(this.candidateConstructorsCache) {candidateConstructors = (Constructor[])this.candidateConstructorsCache.get(beanClass);if (candidateConstructors == null) {Constructor<?>[] rawCandidates;try {
//通过反射获取beanClass中所有声明的构造函数rawCandidates = beanClass.getDeclaredConstructors();} catch (Throwable ex) {throw new BeanCreationException(beanName, "Resolution of declared constructors on bean Class [" + beanClass.getName() + "] from ClassLoader [" + String.valueOf(beanClass.getClassLoader()) + "] failed", ex);}
/**
初始化变量：
candidates: 存储候选构造函数的列表。
requiredConstructor: 标记带有@Autowired(required=true)注解的构造函数。
defaultConstructor: 标记无参构造函数。
primaryConstructor: 通过BeanUtils.findPrimaryConstructor找到的主构造函数。
nonSyntheticConstructors: 统计非合成构造函数的数量。**/List<Constructor<?>> candidates = new ArrayList(rawCandidates.length);Constructor<?> requiredConstructor = null;Constructor<?> defaultConstructor = null;Constructor<?> primaryConstructor = BeanUtils.findPrimaryConstructor(beanClass);int nonSyntheticConstructors = 0;/**
过滤合成构造函数: 合成构造函数（如内部类的构造函数）通常不需要处理。
查找@Autowired注解: 通过findAutowiredAnnotation方法检查构造函数是否带有@Autowired注解。
处理无参构造函数: 如果构造函数没有参数，则标记为defaultConstructor。**/for(Constructor<?> candidate : rawCandidates) {if (!candidate.isSynthetic()) {++nonSyntheticConstructors;} else if (primaryConstructor != null) {continue;}MergedAnnotation<?> ann = this.findAutowiredAnnotation(candidate);if (ann == null) {Class<?> userClass = ClassUtils.getUserClass(beanClass);if (userClass != beanClass) {try {Constructor<?> superCtor = userClass.getDeclaredConstructor(candidate.getParameterTypes());ann = this.findAutowiredAnnotation(superCtor);} catch (NoSuchMethodException var19) {}}}if (ann != null) {if (requiredConstructor != null) {String var23 = String.valueOf(candidate);throw new BeanCreationException(beanName, "Invalid autowire-marked constructor: " + var23 + ". Found constructor with 'required' Autowired annotation already: " + String.valueOf(requiredConstructor));}boolean required = this.determineRequiredStatus(ann);if (required) {if (!candidates.isEmpty()) {String var10003 = String.valueOf(candidates);throw new BeanCreationException(beanName, "Invalid autowire-marked constructors: " + var10003 + ". Found constructor with 'required' Autowired annotation: " + String.valueOf(candidate));}requiredConstructor = candidate;}candidates.add(candidate);} else if (candidate.getParameterCount() == 0) {defaultConstructor = candidate;}}/**优先选择带有@Autowired注解的构造函数。
如果没有合适的构造函数，则根据以下规则选择：
如果只有一个构造函数且带参数，则选择该构造函数。
如果有两个非合成构造函数（主构造函数和无参构造函数），则选择它们。
如果只有一个非合成构造函数（主构造函数），则选择它。
否则，返回空数组。**/if (!candidates.isEmpty()) {if (requiredConstructor == null) {if (defaultConstructor != null) {candidates.add(defaultConstructor);} else if (candidates.size() == 1 && this.logger.isInfoEnabled()) {this.logger.info("Inconsistent constructor declaration on bean with name '" + beanName + "': single autowire-marked constructor flagged as optional - this constructor is effectively required since there is no default constructor to fall back to: " + String.valueOf(candidates.get(0)));}}candidateConstructors = (Constructor[])candidates.toArray(EMPTY_CONSTRUCTOR_ARRAY);} else if (rawCandidates.length == 1 && rawCandidates[0].getParameterCount() > 0) {candidateConstructors = new Constructor[]{rawCandidates[0]};} else if (nonSyntheticConstructors == 2 && primaryConstructor != null && defaultConstructor != null && !primaryConstructor.equals(defaultConstructor)) {candidateConstructors = new Constructor[]{primaryConstructor, defaultConstructor};} else if (nonSyntheticConstructors == 1 && primaryConstructor != null) {candidateConstructors = new Constructor[]{primaryConstructor};} else {candidateConstructors = EMPTY_CONSTRUCTOR_ARRAY;}
//将最终确定的候选构造函数存入缓存，避免重复计算。this.candidateConstructorsCache.put(beanClass, candidateConstructors);}}}return candidateConstructors.length > 0 ? candidateConstructors : null;}