org.springframework.messaging.handler.annotation.support

Class AbstractNamedValueMethodArgumentResolver

java.lang.Object

org.springframework.messaging.handler.annotation.support.AbstractNamedValueMethodArgumentResolver

All Implemented Interfaces:

HandlerMethodArgumentResolver

Direct Known Subclasses:

DestinationVariableMethodArgumentResolver, HeaderMethodArgumentResolver

public abstract class AbstractNamedValueMethodArgumentResolver
extends Object
implements HandlerMethodArgumentResolver

Abstract base class for resolving method arguments from a named value. Message headers, and path variables are examples of named values. Each may have a name, a required flag, and a default value.

Subclasses define how to do the following:

• Obtain named value information for a method parameter
• Resolve names into argument values
• Handle missing argument values when argument values are required
• Optionally handle a resolved value

A default value string can contain ${...} placeholders and Spring Expression Language #{...} expressions. For this to work a ConfigurableBeanFactory must be supplied to the class constructor.

A ConversionService may be used to apply type conversion to the resolved argument value if it doesn't match the method parameter type.

Since:

4.0

Author:

Rossen Stoyanchev, Juergen Hoeller

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	AbstractNamedValueMethodArgumentResolver.NamedValueInfo Represents the information about a named value, including name, whether it's required and a default value.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractNamedValueMethodArgumentResolver(ConversionService cs, ConfigurableBeanFactory beanFactory) Constructor with a ConversionService and a BeanFactory.

Method Summary

Modifier and Type	Method and Description
protected abstract AbstractNamedValueMethodArgumentResolver.NamedValueInfo	createNamedValueInfo(MethodParameter parameter) Create the AbstractNamedValueMethodArgumentResolver.NamedValueInfo object for the given method parameter.
protected abstract void	handleMissingValue(String name, MethodParameter parameter, Message<?> message) Invoked when a named value is required, but resolveArgumentInternal(MethodParameter, Message, String) returned null and there is no default value.
protected void	handleResolvedValue(Object arg, String name, MethodParameter parameter, Message<?> message) Invoked after a value is resolved.
Object	resolveArgument(MethodParameter parameter, Message<?> message) Resolves a method parameter into an argument value from a given message.
protected abstract Object	resolveArgumentInternal(MethodParameter parameter, Message<?> message, String name) Resolves the given parameter type and value name into an argument value.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver

supportsParameter

Constructor Detail

AbstractNamedValueMethodArgumentResolver

protected AbstractNamedValueMethodArgumentResolver(ConversionService cs,
                                                   @Nullable
                                                   ConfigurableBeanFactory beanFactory)

Constructor with a ConversionService and a BeanFactory.

Parameters:

cs - conversion service for converting values to match the target method parameter type

beanFactory - a bean factory to use for resolving ${...} placeholder and #{...} SpEL expressions in default values, or null if default values are not expected to contain expressions

Method Detail

resolveArgument

@Nullable
public Object resolveArgument(MethodParameter parameter,
                                        Message<?> message)
                                 throws Exception

Description copied from interface: HandlerMethodArgumentResolver

Resolves a method parameter into an argument value from a given message.

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.

message - the currently processed message

Returns:

the resolved argument value, or null

Throws:

Exception - in case of errors with the preparation of argument values

createNamedValueInfo

protected abstract AbstractNamedValueMethodArgumentResolver.NamedValueInfo createNamedValueInfo(MethodParameter parameter)

Create the AbstractNamedValueMethodArgumentResolver.NamedValueInfo object for the given method parameter. Implementations typically retrieve the method annotation by means of MethodParameter.getParameterAnnotation(Class).

Parameters:

parameter - the method parameter

Returns:

the named value information

resolveArgumentInternal

@Nullable
protected abstract Object resolveArgumentInternal(MethodParameter parameter,
                                                            Message<?> message,
                                                            String name)
                                                     throws Exception

Resolves the given parameter type and value name into an argument value.

Parameters:

parameter - the method parameter to resolve to an argument value

message - the current request

name - the name of the value being resolved

Returns:

the resolved argument. May be null

Throws:

Exception - in case of errors

handleMissingValue

protected abstract void handleMissingValue(String name,
                                           MethodParameter parameter,
                                           Message<?> message)

Invoked when a named value is required, but resolveArgumentInternal(MethodParameter, Message, String) returned null and there is no default value. Subclasses typically throw an exception in this case.

Parameters:

name - the name for the value

parameter - the method parameter

message - the message being processed

handleResolvedValue

protected void handleResolvedValue(Object arg,
                                   String name,
                                   MethodParameter parameter,
                                   Message<?> message)

Invoked after a value is resolved.

Parameters:

arg - the resolved argument value

name - the argument name

parameter - the argument parameter type

message - the message