Binder Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/Binder.java lines 61–696

public class Binder {

	private static final Set<Class<?>> NON_BEAN_CLASSES = Collections
		.unmodifiableSet(new HashSet<>(Arrays.asList(Object.class, Class.class)));

	private final Iterable<ConfigurationPropertySource> sources;

	private final PlaceholdersResolver placeholdersResolver;

	private final BindConverter bindConverter;

	private final BindHandler defaultBindHandler;

	private final Map<@Nullable BindMethod, List<DataObjectBinder>> dataObjectBinders;

	private final Map<Object, Object> cache = new ConcurrentReferenceHashMap<>();

	private final ConfigurationPropertyCaching configurationPropertyCaching;

	/**
	 * Create a new {@link Binder} instance for the specified sources. A
	 * {@link DefaultFormattingConversionService} will be used for all conversion.
	 * @param sources the sources used for binding
	 */
	public Binder(ConfigurationPropertySource... sources) {
		this(sourcesAsList(sources), null, null, null);
	}

	private static List<ConfigurationPropertySource> sourcesAsList(ConfigurationPropertySource[] sources) {
		Assert.notNull(sources, "'sources' must not be null");
		return Arrays.asList(sources);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources. A
	 * {@link DefaultFormattingConversionService} will be used for all conversion.
	 * @param sources the sources used for binding
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources) {
		this(sources, null, null, null);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver) {
		this(sources, placeholdersResolver, null, null);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 * @param conversionService the conversion service to convert values (or {@code null}
	 * to use {@link ApplicationConversionService})
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver,
			@Nullable ConversionService conversionService) {
		this(sources, placeholdersResolver, conversionService, null);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 * @param conversionService the conversion service to convert values (or {@code null}
	 * to use {@link ApplicationConversionService})
	 * @param propertyEditorInitializer initializer used to configure the property editors
	 * that can convert values (or {@code null} if no initialization is required). Often
	 * used to call {@link ConfigurableListableBeanFactory#copyRegisteredEditorsTo}.
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver,
			@Nullable ConversionService conversionService,
			@Nullable Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
		this(sources, placeholdersResolver, conversionService, propertyEditorInitializer, null);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 * @param conversionService the conversion service to convert values (or {@code null}
	 * to use {@link ApplicationConversionService})
	 * @param propertyEditorInitializer initializer used to configure the property editors
	 * that can convert values (or {@code null} if no initialization is required). Often
	 * used to call {@link ConfigurableListableBeanFactory#copyRegisteredEditorsTo}.
	 * @param defaultBindHandler the default bind handler to use if none is specified when
	 * binding
	 * @since 2.2.0
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver,
			@Nullable ConversionService conversionService,
			@Nullable Consumer<PropertyEditorRegistry> propertyEditorInitializer,
			@Nullable BindHandler defaultBindHandler) {
		this(sources, placeholdersResolver, conversionService, propertyEditorInitializer, defaultBindHandler, null);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 * @param conversionService the conversion service to convert values (or {@code null}
	 * to use {@link ApplicationConversionService})
	 * @param propertyEditorInitializer initializer used to configure the property editors
	 * that can convert values (or {@code null} if no initialization is required). Often
	 * used to call {@link ConfigurableListableBeanFactory#copyRegisteredEditorsTo}.
	 * @param defaultBindHandler the default bind handler to use if none is specified when
	 * binding
	 * @param constructorProvider the constructor provider which provides the bind
	 * constructor to use when binding
	 * @since 2.2.1
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver,
			@Nullable ConversionService conversionService,
			@Nullable Consumer<PropertyEditorRegistry> propertyEditorInitializer,
			@Nullable BindHandler defaultBindHandler, @Nullable BindConstructorProvider constructorProvider) {
		this(sources, placeholdersResolver,
				(conversionService != null) ? Collections.singletonList(conversionService)
						: (List<ConversionService>) null,
				propertyEditorInitializer, defaultBindHandler, constructorProvider);
	}

	/**
	 * Create a new {@link Binder} instance for the specified sources.
	 * @param sources the sources used for binding
	 * @param placeholdersResolver strategy to resolve any property placeholders
	 * @param conversionServices the conversion services to convert values (or
	 * {@code null} to use {@link ApplicationConversionService})
	 * @param propertyEditorInitializer initializer used to configure the property editors
	 * that can convert values (or {@code null} if no initialization is required). Often
	 * used to call {@link ConfigurableListableBeanFactory#copyRegisteredEditorsTo}.
	 * @param defaultBindHandler the default bind handler to use if none is specified when
	 * binding
	 * @param constructorProvider the constructor provider which provides the bind
	 * constructor to use when binding
	 * @since 2.5.0
	 */
	public Binder(Iterable<ConfigurationPropertySource> sources, @Nullable PlaceholdersResolver placeholdersResolver,
			@Nullable List<ConversionService> conversionServices,
			@Nullable Consumer<PropertyEditorRegistry> propertyEditorInitializer,
			@Nullable BindHandler defaultBindHandler, @Nullable 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.configurationPropertyCaching = ConfigurationPropertyCaching.get(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;
		Map<@Nullable BindMethod, List<DataObjectBinder>> dataObjectBinders = new HashMap<>();
		dataObjectBinders.put(BindMethod.VALUE_OBJECT, List.of(valueObjectBinder));
		dataObjectBinders.put(BindMethod.JAVA_BEAN, List.of(javaBeanBinder));
		dataObjectBinders.put(null, List.of(valueObjectBinder, javaBeanBinder));
		this.dataObjectBinders = Collections.unmodifiableMap(dataObjectBinders);
	}

	/**
	 * Bind the specified target {@link Class} using this binder's
	 * {@link ConfigurationPropertySource property sources}.
	 * @param name the configuration property name to bind
	 * @param target the target class
	 * @param <T> the bound type
	 * @return the binding result (never {@code null})
	 * @see #bind(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> BindResult<T> bind(String name, Class<T> target) {
		return bind(name, Bindable.of(target));
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param <T> the bound type
	 * @return the binding result (never {@code null})
	 * @see #bind(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> BindResult<T> bind(String name, Bindable<T> target) {
		return bind(ConfigurationPropertyName.of(name), target, null);
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param <T> the bound type
	 * @return the binding result (never {@code null})
	 * @see #bind(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> BindResult<T> bind(ConfigurationPropertyName name, Bindable<T> target) {
		return bind(name, target, null);
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param handler the bind handler (may be {@code null})
	 * @param <T> the bound type
	 * @return the binding result (never {@code null})
	 */
	public <T> BindResult<T> bind(String name, Bindable<T> target, @Nullable BindHandler handler) {
		return bind(ConfigurationPropertyName.of(name), target, handler);
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param handler the bind handler (may be {@code null})
	 * @param <T> the bound type
	 * @return the binding result (never {@code null})
	 */
	public <T> BindResult<T> bind(ConfigurationPropertyName name, Bindable<T> target, @Nullable BindHandler handler) {
		T bound = bind(name, target, handler, false);
		return BindResult.of(bound);
	}

	/**
	 * Bind the specified target {@link Class} using this binder's
	 * {@link ConfigurationPropertySource property sources} or create a new instance of
	 * the specified target {@link Class} if the result of the binding is {@code null}.
	 * @param name the configuration property name to bind
	 * @param target the target class
	 * @param <T> the bound type
	 * @return the bound or created object
	 * @since 2.2.0
	 * @see #bind(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> T bindOrCreate(String name, Class<T> target) {
		return bindOrCreate(name, Bindable.of(target));
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources} or create a new instance using
	 * the type of the {@link Bindable} if the result of the binding is {@code null}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param <T> the bound type
	 * @return the bound or created object
	 * @since 2.2.0
	 * @see #bindOrCreate(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> T bindOrCreate(String name, Bindable<T> target) {
		return bindOrCreate(ConfigurationPropertyName.of(name), target, null);
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources} or create a new instance using
	 * the type of the {@link Bindable} if the result of the binding is {@code null}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param handler the bind handler
	 * @param <T> the bound type
	 * @return the bound or created object
	 * @since 2.2.0
	 * @see #bindOrCreate(ConfigurationPropertyName, Bindable, BindHandler)
	 */
	public <T> T bindOrCreate(String name, Bindable<T> target, BindHandler handler) {
		return bindOrCreate(ConfigurationPropertyName.of(name), target, handler);
	}

	/**
	 * Bind the specified target {@link Bindable} using this binder's
	 * {@link ConfigurationPropertySource property sources} or create a new instance using
	 * the type of the {@link Bindable} if the result of the binding is {@code null}.
	 * @param name the configuration property name to bind
	 * @param target the target bindable
	 * @param handler the bind handler (may be {@code null})
	 * @param <T> the bound or created type
	 * @return the bound or created object
	 * @since 2.2.0
	 */
	@SuppressWarnings("NullAway") // https://github.com/uber/NullAway/issues/1232
	public <T> T bindOrCreate(ConfigurationPropertyName name, Bindable<T> target, @Nullable BindHandler handler) {
		return bind(name, target, handler, true);
	}

	@Contract("_, _, _, true -> !null")
	private <T> @Nullable T bind(ConfigurationPropertyName name, Bindable<T> target, @Nullable 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);
	}

	@Contract("_, _, _, _, _, true -> !null")
	private <T> @Nullable T bind(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, boolean allowRecursiveBinding, boolean create) {
		try (ConfigurationPropertyCaching.CacheOverride cacheOverride = this.configurationPropertyCaching.override()) {
			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);
			}
		}
	}

	@Contract("_, _, _, _, _, true -> null")
	private <T> @Nullable T handleBindResult(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, @Nullable Object result, boolean create) throws Exception {
		if (result != null) {
			result = handler.onSuccess(name, target, context, result);
			result = context.getConverter().convert(result, target);
		}
		if (result == null && create) {
			result = fromDataObjectBinders(target.getBindMethod(),
					(dataObjectBinder) -> dataObjectBinder.create(target, context));
			if (result == null) {
				IllegalStateException ex = new IllegalStateException(
						"Unable to create instance for " + target.getType());
				List<DataObjectBinder> dataObjectBinders = this.dataObjectBinders.get(target.getBindMethod());
				Assert.state(dataObjectBinders != null, "'dataObjectBinders' must not be null");
				dataObjectBinders
					.forEach((dataObjectBinder) -> dataObjectBinder.onUnableToCreateInstance(target, context, ex));
				throw ex;
			}
			result = handler.onCreate(name, target, context, result);
			result = context.getConverter().convert(result, target);
		}
		handler.onFinish(name, target, context, result);
		return context.getConverter().convert(result, target);
	}

	private <T> @Nullable T handleBindError(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, Exception error) {
		try {
			Object result = handler.onFailure(name, target, context, error);
			return context.getConverter().convert(result, target);
		}
		catch (Exception ex) {
			if (ex instanceof BindException bindException) {
				throw bindException;
			}
			throw new BindException(name, target, context.getConfigurationProperty(), ex);
		}
	}

	private <T> @Nullable Object bindObject(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, boolean allowRecursiveBinding) {
		ConfigurationProperty property = findProperty(name, target, context);
		if (property == null && context.depth != 0 && containsNoDescendantOf(context.getSources(), name)) {
			return null;
		}
		AggregateBinder<?> aggregateBinder = getAggregateBinder(target, context);
		if (aggregateBinder != null) {
			return bindAggregate(name, target, handler, context, aggregateBinder);
		}
		if (property != null) {
			try {
				return bindProperty(target, context, property);
			}
			catch (ConverterNotFoundException ex) {
				// We might still be able to bind it using the recursive binders
				Object instance = bindDataObject(name, target, handler, context, allowRecursiveBinding);
				if (instance != null) {
					return instance;
				}
				throw ex;
			}
		}
		return bindDataObject(name, target, handler, context, allowRecursiveBinding);
	}

	private @Nullable AggregateBinder<?> getAggregateBinder(Bindable<?> target, Context context) {
		Class<?> resolvedType = target.getType().resolve(Object.class);
		if (Map.class.isAssignableFrom(resolvedType)) {
			return new MapBinder(context);
		}
		if (Collection.class.isAssignableFrom(resolvedType)) {
			return new CollectionBinder(context);
		}
		if (target.getType().isArray()) {
			return new ArrayBinder(context);
		}
		return null;
	}

	private <T> @Nullable Object bindAggregate(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, AggregateBinder<?> aggregateBinder) {
		AggregateElementBinder elementBinder = (itemName, itemTarget, source) -> {
			boolean allowRecursiveBinding = aggregateBinder.isAllowRecursiveBinding(source);
			Supplier<?> supplier = () -> bind(itemName, itemTarget, handler, context, allowRecursiveBinding, false);
			return context.withSource(source, supplier);
		};
		Supplier<@Nullable Object> supplier = () -> aggregateBinder.bind(name, target, elementBinder);
		return context.withIncreasedDepth(supplier);
	}

	private <T> @Nullable ConfigurationProperty findProperty(ConfigurationPropertyName name, Bindable<T> target,
			Context context) {
		if (name.isEmpty() || target.hasBindRestriction(BindRestriction.NO_DIRECT_PROPERTY)) {
			return null;
		}
		for (ConfigurationPropertySource source : context.getSources()) {
			ConfigurationProperty property = source.getConfigurationProperty(name);
			if (property != null) {
				return property;
			}
		}
		return null;
	}

	private <T> @Nullable Object bindProperty(Bindable<T> target, Context context, ConfigurationProperty property) {
		context.setConfigurationProperty(property);
		Object result = property.getValue();
		result = this.placeholdersResolver.resolvePlaceholders(result);
		result = context.getConverter().convert(result, target);
		return result;
	}

	private @Nullable 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);
		BindMethod bindMethod = target.getBindMethod();
		if (!allowRecursiveBinding && context.isBindingDataObject(type)) {
			return null;
		}
		DataObjectPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(name.append(propertyName),
				propertyTarget, handler, context, false, false);
		Supplier<@Nullable Object> supplier = () -> fromDataObjectBinders(bindMethod,
				(dataObjectBinder) -> dataObjectBinder.bind(name, target, context, propertyBinder));
		return context.withDataObject(type, supplier);
	}

	private @Nullable Object fromDataObjectBinders(@Nullable BindMethod bindMethod,
			Function<DataObjectBinder, @Nullable Object> operation) {
		List<DataObjectBinder> dataObjectBinders = this.dataObjectBinders.get(bindMethod);
		Assert.state(dataObjectBinders != null, "'dataObjectBinders' must not be null");
		for (DataObjectBinder dataObjectBinder : dataObjectBinders) {
			Object bound = operation.apply(dataObjectBinder);
			if (bound != null) {
				return bound;
			}
		}
		return null;
	}

	private boolean isUnbindableBean(ConfigurationPropertyName name, Bindable<?> target, Context context) {
		for (ConfigurationPropertySource source : context.getSources()) {
			if (source.containsDescendantOf(name) == ConfigurationPropertyState.PRESENT) {
				// We know there are properties to bind so we can't bypass anything
				return false;
			}
		}
		Class<?> resolved = target.getType().resolve(Object.class);
		if (resolved.isPrimitive() || NON_BEAN_CLASSES.contains(resolved)) {
			return true;
		}
		return resolved.getName().startsWith("java.");
	}

	private boolean containsNoDescendantOf(Iterable<ConfigurationPropertySource> sources,
			ConfigurationPropertyName name) {
		for (ConfigurationPropertySource source : sources) {
			if (source.containsDescendantOf(name) != ConfigurationPropertyState.ABSENT) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Create a new {@link Binder} instance from the specified environment.
	 * @param environment the environment source (must have attached
	 * {@link ConfigurationPropertySources})
	 * @return a {@link Binder} instance
	 */
	public static Binder get(Environment environment) {
		return get(environment, null);
	}

	/**
	 * Create a new {@link Binder} instance from the specified environment.
	 * @param environment the environment source (must have attached
	 * {@link ConfigurationPropertySources})
	 * @param defaultBindHandler the default bind handler to use if none is specified when
	 * binding
	 * @return a {@link Binder} instance
	 * @since 2.2.0
	 */
	public static Binder get(Environment environment, @Nullable BindHandler defaultBindHandler) {
		Iterable<ConfigurationPropertySource> sources = ConfigurationPropertySources.get(environment);
		PropertySourcesPlaceholdersResolver placeholdersResolver = new PropertySourcesPlaceholdersResolver(environment);
		return new Binder(sources, placeholdersResolver, null, null, defaultBindHandler);
	}

	/**
	 * Context used when binding and the {@link BindContext} implementation.
	 */
	final class Context implements BindContext {

		private int depth;

		private final List<ConfigurationPropertySource> source = Arrays.asList((ConfigurationPropertySource) null);

		private int sourcePushCount;

		private final Deque<Class<?>> dataObjectBindings = new ArrayDeque<>();

		private final Deque<Class<?>> constructorBindings = new ArrayDeque<>();

		private @Nullable ConfigurationProperty configurationProperty;

		private void increaseDepth() {
			this.depth++;
		}

		private void decreaseDepth() {
			this.depth--;
		}

		private <T> T withSource(@Nullable ConfigurationPropertySource source, Supplier<T> supplier) {
			if (source == null) {
				return supplier.get();
			}
			ConfigurationPropertySource previous = this.source.get(0);
			this.source.set(0, source);
			this.sourcePushCount++;
			try {
				return supplier.get();
			}
			finally {
				this.sourcePushCount--;
				this.source.set(0, previous);
			}
		}

		private <T> @Nullable T withDataObject(Class<?> type, Supplier<@Nullable T> supplier) {
			this.dataObjectBindings.push(type);
			try {
				return withIncreasedDepth(supplier);
			}
			finally {
				this.dataObjectBindings.pop();
			}
		}

		private boolean isBindingDataObject(Class<?> type) {
			return this.dataObjectBindings.contains(type);
		}

		private <T> @Nullable T withIncreasedDepth(Supplier<@Nullable T> supplier) {
			increaseDepth();
			try {
				return supplier.get();
			}
			finally {
				decreaseDepth();
			}
		}

		void setConfigurationProperty(ConfigurationProperty configurationProperty) {
			this.configurationProperty = configurationProperty;
		}

		void clearConfigurationProperty() {
			this.configurationProperty = null;
		}

		void pushConstructorBoundTypes(Class<?> value) {
			this.constructorBindings.push(value);
		}

		boolean isNestedConstructorBinding() {
			return !this.constructorBindings.isEmpty();
		}

		void popConstructorBoundTypes() {
			this.constructorBindings.pop();
		}

		PlaceholdersResolver getPlaceholdersResolver() {
			return Binder.this.placeholdersResolver;
		}

		BindConverter getConverter() {
			return Binder.this.bindConverter;
		}

		Map<Object, Object> getCache() {
			return Binder.this.cache;
		}

		@Override
		public Binder getBinder() {
			return Binder.this;
		}

		@Override
		public int getDepth() {
			return this.depth;
		}

		@Override
		public Iterable<ConfigurationPropertySource> getSources() {
			if (this.sourcePushCount > 0) {
				return this.source;
			}
			return Binder.this.sources;
		}

		@Override
		public @Nullable ConfigurationProperty getConfigurationProperty() {
			return this.configurationProperty;
		}

	}

}