springBoot源码汇总

SpringFactoriesLoader

示例位置 SpringApplication#getSpringFactoriesInstances
加载spring.factroies下的初始化类

 ClassLoader classLoader = this.getClassLoader();
        Set names = new LinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
        List instances = this.createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
        AnnotationAwareOrderComparator.sort(instances);
        return instances;

说明：
SpringFactoriesLoader.loadFactoryNames 加载type为spring.factroies 下的 class的key值

List loadFactoryNames(Class factoryType, @Nullable ClassLoader classLoader)

ClassUtils .BeanUtils

示例位置 SpringApplication#createSpringFactoriesInstances

  try {
                Class instanceClass = ClassUtils.forName(name, classLoader);
                Assert.isAssignable(type, instanceClass);
                Constructor constructor = instanceClass.getDeclaredConstructor(parameterTypes);
                T instance = BeanUtils.instantiateClass(constructor, args);
                instances.add(instance);
            } catch (Throwable var12) {
                throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, var12);
            }

ClassUtils.forName，name为加载类的全路径名称，通过ClassUtils.forName加载对应的类
通过 instanceClass.getDeclaredConstructor(parameterTypes); 表示传入无参的构造参数
示例此处的值为：new Class[0] ，

new Class[0]表示有零个元素的Class数组，即空数组，与传入null结果是一样的，都表示取得无参构造方法。
但是使用该方式可以避免抛出空异常。

BeanUtils.instantiateClass(constructor, args); 通过构造函数，入参实例化一个对象

org.springframework.util.ClassUtils#forName

public static Class forName(String name, @Nullable ClassLoader classLoader) throws ClassNotFoundException, LinkageError

org.springframework.beans.BeanUtils#instantiateClass

 instantiateClass(Constructor ctor, Object... args) 

自定义函数入参

函数参数调用方

示例位置：SpringApplicationRunListeners#starting

 this.doWithListeners("spring.boot.application.starting", (listener) -> {
            listener.starting(bootstrapContext);
        }, (step) -> {
            if (mainApplicationClass != null) {
                step.tag("mainApplicationClass", mainApplicationClass.getName());
            }
        });

函数参数定义方

   private void doWithListeners(String stepName, Consumer listenerAction, Consumer stepAction) {
        StartupStep step = this.applicationStartup.start(stepName);
        this.listeners.forEach(listenerAction);
        if (stepAction != null) {
            stepAction.accept(step);
        }
        step.end();
    }
}