记录 - SpringBoot 自动配置的坑 isXXX失效

场景

使用 SpringBoot 的自动配置。

@Data
@Component
@ConfigurationProperties(prefix = "xxx")
private Boolean isSandbox = false;

配置文件中: xxxx.isSandbox =true
但是并没有生效。我虽然阅读spring源码，但是springBoot源码我没有读，所以我相信源码一定会带来答案。

从注释入手

@ConfigurationProperties(prefix = “xxx”)
像赋值这种事，应该是在bean实例化的时候做的，所以点开注释使用者应该去找XXXPostProcessor类，果然我找到了ConfigurationPropertiesBindingPostProcessor类，点开。

	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		bind(ConfigurationPropertiesBean.get(this.applicationContext, bean, beanName));
		return bean;
	}

	private void bind(ConfigurationPropertiesBean bean) {
		if (bean == null || hasBoundValueObject(bean.getName())) {
			return;
		}
		Assert.state(bean.getBindMethod() == BindMethod.JAVA_BEAN, "Cannot bind @ConfigurationProperties for bean '"
				+ bean.getName() + "'. Ensure that @ConstructorBinding has not been applied to regular bean");
		try {
			this.binder.bind(bean);
		}
		catch (Exception ex) {
			throw new ConfigurationPropertiesBindException(bean, ex);
		}
	}

发现bind 似乎就是我想知道的。

继续往下

	BindResult<?> bind(ConfigurationPropertiesBean propertiesBean) {
		Bindable<?> target = propertiesBean.asBindTarget();
		ConfigurationProperties annotation = propertiesBean.getAnnotation();
		BindHandler bindHandler = getBindHandler(target, annotation);
		return getBinder().bind(annotation.prefix(), target, bindHandler);
	}

这段代码应是获取 bindHandler，随后去绑定配置值。一路next

	private <T> T bind(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler, boolean create) {
		Assert.notNull(name, "Name must not be null");
		Assert.notNull(target, "Target must not be null");
		handler = (handler != null) ? handler : this.defaultBindHandler;
		Context context = new Context();
		return bind(name, target, handler, context, false, create);
	}

private <T> T bind(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler, Context context,
			boolean allowRecursiveBinding, boolean create) {
		try {
			Bindable<T> replacementTarget = handler.onStart(name, target, context);
			if (replacementTarget == null) {
				return handleBindResult(name, target, handler, context, null, create);
			}
			target = replacementTarget;
			Object bound = bindObject(name, target, handler, context, allowRecursiveBinding);
			return handleBindResult(name, target, handler, context, bound, create);
		}
		catch (Exception ex) {
			return handleBindError(name, target, handler, context, ex);
		}
	}

一路next，发现正在遍历 dataObjectBinder 我们找到Binder构造方法，看看里面有没有定义这些dataObjectBinders

private Object bindDataObject(ConfigurationPropertyName name, Bindable<?> target, BindHandler handler,
			Context context, boolean allowRecursiveBinding) {
		if (isUnbindableBean(name, target, context)) {
			return null;
		}
		Class<?> type = target.getType().resolve(Object.class);
		if (!allowRecursiveBinding && context.isBindingDataObject(type)) {
			return null;
		}
		DataObjectPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(name.append(propertyName),
				propertyTarget, handler, context, false, false);
		return context.withDataObject(type, () -> {
			for (DataObjectBinder dataObjectBinder : this.dataObjectBinders) {
				Object instance = dataObjectBinder.bind(name, target, context, propertyBinder);
				if (instance != null) {
					return instance;
				}
			}
			return null;
		});
	}

我们发现：

public Binder(Iterable<ConfigurationPropertySource> sources, PlaceholdersResolver placeholdersResolver,
			List<ConversionService> conversionServices, Consumer<PropertyEditorRegistry> propertyEditorInitializer,
			BindHandler defaultBindHandler, BindConstructorProvider constructorProvider) {
		Assert.notNull(sources, "Sources must not be null");
		for (ConfigurationPropertySource source : sources) {
			Assert.notNull(source, "Sources must not contain null elements");
		}
		this.sources = sources;
		this.placeholdersResolver = (placeholdersResolver != null) ? placeholdersResolver : PlaceholdersResolver.NONE;
		this.bindConverter = BindConverter.get(conversionServices, propertyEditorInitializer);
		this.defaultBindHandler = (defaultBindHandler != null) ? defaultBindHandler : BindHandler.DEFAULT;
		if (constructorProvider == null) {
			constructorProvider = BindConstructorProvider.DEFAULT;
		}
		ValueObjectBinder valueObjectBinder = new ValueObjectBinder(constructorProvider);
		JavaBeanBinder javaBeanBinder = JavaBeanBinder.INSTANCE;
		this.dataObjectBinders = Collections.unmodifiableList(Arrays.asList(valueObjectBinder, javaBeanBinder));
	}

有两个Binder，一个是ValueObjectBinder 一个是JavaBeanBinder ，进去看看 bind 方法都做了什么
ValueObjectBinder 的

	@Override
	public <T> T bind(ConfigurationPropertyName name, Bindable<T> target, Binder.Context context,
			DataObjectPropertyBinder propertyBinder) {
		ValueObject<T> valueObject = ValueObject.get(target, this.constructorProvider, context);
		if (valueObject == null) {
			return null;
		}
		context.pushConstructorBoundTypes(target.getType().resolve());
		List<ConstructorParameter> parameters = valueObject.getConstructorParameters();
		List<Object> args = new ArrayList<>(parameters.size());
		boolean bound = false;
		for (ConstructorParameter parameter : parameters) {
			Object arg = parameter.bind(propertyBinder);
			bound = bound || arg != null;
			arg = (arg != null) ? arg : getDefaultValue(context, parameter);
			args.add(arg);
		}
		context.clearConfigurationProperty();
		context.popConstructorBoundTypes();
		return bound ? valueObject.instantiate(args) : null;
	}

这大概的意思是有值就放没有就默认值的，我猜想这应该是 ${xxx} 这种赋值的。

所以我们应该去看给类赋值的

再Bind里一路next发现

protected void addProperties(Method[] declaredMethods, Field[] declaredFields) {
			for (int i = 0; i < declaredMethods.length; i++) {
				if (!isCandidate(declaredMethods[i])) {
					declaredMethods[i] = null;
				}
			}
			for (Method method : declaredMethods) {
				addMethodIfPossible(method, "is", 0, BeanProperty::addGetter);
			}
			for (Method method : declaredMethods) {
				addMethodIfPossible(method, "get", 0, BeanProperty::addGetter);
			}
			for (Method method : declaredMethods) {
				addMethodIfPossible(method, "set", 1, BeanProperty::addSetter);
			}
			for (Field field : declaredFields) {
				addField(field);
			}
		}

顿时一切都明白了，因为这个字段叫isSandbox ，他的方法也叫isSandbox ，如果想要它生效,把它换成大布尔类型，或者改名为setIsSandbox.]

结束

2023/12/21 - 记录