Package org.springframework.web.method.annotation

Class ModelAttributeMethodProcessor

java.lang.Object

org.springframework.web.method.annotation.ModelAttributeMethodProcessor

All Implemented Interfaces:

HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler

Direct Known Subclasses:

ServletModelAttributeMethodProcessor

public class ModelAttributeMethodProcessor
extends Object
implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler

Resolve @ModelAttribute annotated method arguments and handle return values from @ModelAttribute annotated methods.

Model attributes are obtained from the model or created with a default constructor (and then added to the model). Once created the attribute is populated via data binding to Servlet request parameters. Validation may be applied if the argument is annotated with @jakarta.validation.Valid. or Spring's own @org.springframework.validation.annotation.Validated.

When this handler is created with annotationNotRequired=true any non-simple type argument and return value is regarded as a model attribute with or without the presence of an @ModelAttribute.

Since:

3.1

Author:

Rossen Stoyanchev, Juergen Hoeller, Sebastien Deleuze, Vladislav Kisel

Field Summary

Fields

Modifier and Type	Field	Description
protected final Log	logger

Constructor Summary

Constructors

Constructor	Description
ModelAttributeMethodProcessor(boolean annotationNotRequired)	Class constructor.

Method Summary

Modifier and Type	Method	Description
protected void	bindRequestParameters(WebDataBinder binder, NativeWebRequest request)	Extension point to bind the request to the target object.
protected Object	constructAttribute(Constructor<?> ctor, String attributeName, MethodParameter parameter, WebDataBinderFactory binderFactory, NativeWebRequest webRequest)	Construct a new attribute instance with the given constructor.
protected Object	createAttribute(String attributeName, MethodParameter parameter, WebDataBinderFactory binderFactory, NativeWebRequest webRequest)	Extension point to create the model attribute if not found in the model, with subsequent parameter binding through bean properties (unless suppressed).
void	handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest)	Add non-null return values to the ModelAndViewContainer.
protected boolean	isBindExceptionRequired(MethodParameter parameter)	Whether to raise a fatal bind exception on validation errors.
protected boolean	isBindExceptionRequired(WebDataBinder binder, MethodParameter parameter)	Whether to raise a fatal bind exception on validation errors.
final Object	resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory)	Resolve the argument from the model or if not found instantiate it with its default if it is available.
Object	resolveConstructorArgument(String paramName, Class<?> paramType, NativeWebRequest request)
boolean	supportsParameter(MethodParameter parameter)	Returns true if the parameter is annotated with ModelAttribute or, if in default resolution mode, for any method parameter that is not a simple type.
boolean	supportsReturnType(MethodParameter returnType)	Return true if there is a method-level @ModelAttribute or, in default resolution mode, for any return value type that is not a simple type.
protected void	validateIfApplicable(WebDataBinder binder, MethodParameter parameter)	Validate the model attribute if applicable.
protected void	validateValueIfApplicable(WebDataBinder binder, MethodParameter parameter, Class<?> targetType, String fieldName, Object value)	Validate the specified candidate value if applicable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

logger

protected final Log logger

Constructor Details

ModelAttributeMethodProcessor

public ModelAttributeMethodProcessor(boolean annotationNotRequired)

Class constructor.

Parameters:

annotationNotRequired - if "true", non-simple method arguments and return values are considered model attributes with or without a @ModelAttribute annotation

Method Details

supportsParameter

public boolean supportsParameter(MethodParameter parameter)

Returns true if the parameter is annotated with ModelAttribute or, if in default resolution mode, for any method parameter that is not a simple type.

Specified by:

supportsParameter in interface HandlerMethodArgumentResolver

Parameters:

parameter - the method parameter to check

Returns:

true if this resolver supports the supplied parameter; false otherwise

resolveArgument

@Nullable
public final Object resolveArgument(MethodParameter parameter,
 @Nullable
 ModelAndViewContainer mavContainer,
 NativeWebRequest webRequest,
 @Nullable
 WebDataBinderFactory binderFactory)
                             throws Exception

Resolve the argument from the model or if not found instantiate it with its default if it is available. The model attribute is then populated with request values via data binding and optionally validated if @java.validation.Valid is present on the argument.

Specified by:

resolveArgument in interface HandlerMethodArgumentResolver

Parameters:

parameter - the method parameter to resolve. This parameter must have previously been passed to HandlerMethodArgumentResolver.supportsParameter(org.springframework.core.MethodParameter) which must have returned true.

mavContainer - the ModelAndViewContainer for the current request

webRequest - the current request

binderFactory - a factory for creating WebDataBinder instances

Returns:

the resolved argument value, or null if not resolvable

Throws:

BindException - if data binding and validation result in an error and the next method parameter is not of type Errors

Exception - if WebDataBinder initialization fails

createAttribute

protected Object createAttribute(String attributeName,
 MethodParameter parameter,
 WebDataBinderFactory binderFactory,
 NativeWebRequest webRequest)
                          throws Exception

Extension point to create the model attribute if not found in the model, with subsequent parameter binding through bean properties (unless suppressed).

The default implementation typically uses the unique public no-arg constructor if available but also handles a "primary constructor" approach for data classes: It understands the JavaBeans ConstructorProperties annotation as well as runtime-retained parameter names in the bytecode, associating request parameters with constructor arguments by name. If no such constructor is found, the default constructor will be used (even if not public), assuming subsequent bean property bindings through setter methods.

Parameters:

attributeName - the name of the attribute (never null)

parameter - the method parameter declaration

binderFactory - for creating WebDataBinder instance

webRequest - the current request

Returns:

the created model attribute (never null)

Throws:

BindException - in case of constructor argument binding failure

Exception - in case of constructor invocation failure

See Also:

• constructAttribute(Constructor, String, MethodParameter, WebDataBinderFactory, NativeWebRequest)
• BeanUtils.findPrimaryConstructor(Class)

constructAttribute

protected Object constructAttribute(Constructor<?> ctor,
 String attributeName,
 MethodParameter parameter,
 WebDataBinderFactory binderFactory,
 NativeWebRequest webRequest)
                             throws Exception

Construct a new attribute instance with the given constructor.

Called from createAttribute(String, MethodParameter, WebDataBinderFactory, NativeWebRequest) after constructor resolution.

Parameters:

ctor - the constructor to use

attributeName - the name of the attribute (never null)

binderFactory - for creating WebDataBinder instance

webRequest - the current request

Returns:

the created model attribute (never null)

Throws:

BindException - in case of constructor argument binding failure

Exception - in case of constructor invocation failure

Since:

5.1

bindRequestParameters

protected void bindRequestParameters(WebDataBinder binder,
 NativeWebRequest request)

Extension point to bind the request to the target object.

Parameters:

binder - the data binder instance to use for the binding

request - the current request

resolveConstructorArgument

@Nullable
public Object resolveConstructorArgument(String paramName,
 Class<?> paramType,
 NativeWebRequest request)
                                  throws Exception

Throws:

Exception

validateIfApplicable

protected void validateIfApplicable(WebDataBinder binder,
 MethodParameter parameter)

Validate the model attribute if applicable.

The default implementation checks for @jakarta.validation.Valid, Spring's Validated, and custom annotations whose name starts with "Valid".

Parameters:

binder - the DataBinder to be used

parameter - the method parameter declaration

See Also:

• DataBinder.validate(Object...)
• SmartValidator.validate(Object, Errors, Object...)

validateValueIfApplicable

protected void validateValueIfApplicable(WebDataBinder binder,
 MethodParameter parameter,
 Class<?> targetType,
 String fieldName,
 @Nullable
 Object value)

Validate the specified candidate value if applicable.

The default implementation checks for @jakarta.validation.Valid, Spring's Validated, and custom annotations whose name starts with "Valid".

Parameters:

binder - the DataBinder to be used

parameter - the method parameter declaration

targetType - the target type

fieldName - the name of the field

value - the candidate value

Since:

5.1

See Also:

• validateIfApplicable(WebDataBinder, MethodParameter)
• SmartValidator.validateValue(Class, String, Object, Errors, Object...)

isBindExceptionRequired

protected boolean isBindExceptionRequired(WebDataBinder binder,
 MethodParameter parameter)

Whether to raise a fatal bind exception on validation errors.

The default implementation delegates to isBindExceptionRequired(MethodParameter).

Parameters:

binder - the data binder used to perform data binding

parameter - the method parameter declaration

Returns:

true if the next method parameter is not of type Errors

See Also:

• isBindExceptionRequired(MethodParameter)

isBindExceptionRequired

protected boolean isBindExceptionRequired(MethodParameter parameter)

Whether to raise a fatal bind exception on validation errors.

Parameters:

parameter - the method parameter declaration

Returns:

true if the next method parameter is not of type Errors

Since:

5.0

supportsReturnType

public boolean supportsReturnType(MethodParameter returnType)

Return true if there is a method-level @ModelAttribute or, in default resolution mode, for any return value type that is not a simple type.

Specified by:

supportsReturnType in interface HandlerMethodReturnValueHandler

Parameters:

returnType - the method return type to check

Returns:

true if this handler supports the supplied return type; false otherwise

handleReturnValue

public void handleReturnValue(@Nullable
 Object returnValue,
 MethodParameter returnType,
 ModelAndViewContainer mavContainer,
 NativeWebRequest webRequest)
                       throws Exception

Add non-null return values to the ModelAndViewContainer.

Specified by:

handleReturnValue in interface HandlerMethodReturnValueHandler

Parameters:

returnValue - the value returned from the handler method

returnType - the type of the return value. This type must have previously been passed to HandlerMethodReturnValueHandler.supportsReturnType(org.springframework.core.MethodParameter) which must have returned true.

mavContainer - the ModelAndViewContainer for the current request

webRequest - the current request

Throws:

Exception - if the return value handling results in an error