org.springframework.validation
Class DataBinder

java.lang.Object
  org.springframework.validation.DataBinder

Direct Known Subclasses:

ServletRequestDataBinder

public class DataBinder

extends Object

Binder that allows for binding property values to a target object. The binding process can be customized through specifying allowed fields, required fields, and custom editors.

Note that there are potential security implications in failing to set an array of allowed fields. In the case of HTTP form POST data for example, malicious clients can attempt to subvert an application by supplying values for fields or properties that do not exist on the form. In some cases this could lead to illegal data being set on command objects or their nested objects. For this reason, it is highly recommended to specify the allowedFields property on the DataBinder.

The binding results can be examined via the Errors interface, available as BindException instance. Missing field errors and property access exceptions will be converted to FieldErrors, collected in the Errors instance, with the following error codes:

• Missing field error: "required"
• Type mismatch error: "typeMismatch"
• Method invocation error: "methodInvocation"

Custom validation errors can be added afterwards. You will typically want to resolve such error codes into proper user-visible error messages; this can be achieved through resolving each error via a MessageSource. The list of message codes to try can be customized through the MessageCodesResolver strategy. DefaultMessageCodesResolver's javadoc gives details on the default resolution rules.

This generic data binder can be used in any sort of environment. It is heavily used by Spring's web binding features, via the subclass ServletRequestDataBinder.

Author:

Rod Johnson, Juergen Hoeller

See Also:

setAllowedFields(java.lang.String[]), setRequiredFields(java.lang.String[]), registerCustomEditor(java.lang.Class, java.beans.PropertyEditor), setMessageCodesResolver(org.springframework.validation.MessageCodesResolver), bind(org.springframework.beans.PropertyValues), getErrors(), DefaultMessageCodesResolver, MessageSource, ServletRequestDataBinder

Field Summary

protected static Log	logger We'll create a lot of DataBinder instances: Let's use a static logger.
static String	METHOD_INVOCATION_ERROR_CODE Error code that a type mismatch error (i.e. a property value not matching the type of the target field) will be registered with: "methodInvocation".
static String	MISSING_FIELD_ERROR_CODE Error code that a missing field error (i.e. a required field not found in the list of property values) will be registered with: "required".
static String	TYPE_MISMATCH_ERROR_CODE Error code that a type mismatch error (i.e. a property value not matching the type of the target field) will be registered with: "typeMismatch".

Constructor Summary

DataBinder(Object target, String objectName)
Create a new DataBinder instance.

Method Summary

void	bind(PropertyValues pvs) Bind the given property values to this binder's target.
Map	close() Close this DataBinder, which may result in throwing a BindException if it encountered any errors
protected BindException	createErrors(Object target, String objectName) Create a new Errors instance for this data binder.
String[]	getAllowedFields() Return the fields that should be allowed for binding.
protected Object[]	getArgumentsForBindingError(String field) Return FieldError arguments for a binding error on the given field.
protected BeanWrapper	getBeanWrapper() Return the underlying BeanWrapper of the Errors object.
BindException	getErrors() Return the Errors instance for this data binder.
String	getObjectName() Return the name of the bound object.
String[]	getRequiredFields() Return the fields that are required for each binding process.
Object	getTarget() Return the wrapped target object.
protected boolean	isAllowed(String field) Return if the given field is allowed for binding.
void	registerCustomEditor(Class requiredType, PropertyEditor propertyEditor) Register the given custom property editor for all properties of the given type.
void	registerCustomEditor(Class requiredType, String field, PropertyEditor propertyEditor) Register the given custom property editor for the given type and field, or for all fields of the given type.
void	setAllowedFields(String[] allowedFields) Register fields that should be allowed for binding.
void	setMessageCodesResolver(MessageCodesResolver messageCodesResolver) Set the strategy to use for resolving errors into message codes.
void	setRequiredFields(String[] requiredFields) Register fields that are required for each binding process.

Methods inherited from class java.lang.Object

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

Field Detail

MISSING_FIELD_ERROR_CODE

public static final String MISSING_FIELD_ERROR_CODE

Error code that a missing field error (i.e. a required field not found in the list of property values) will be registered with: "required".

See Also:

Constant Field Values

TYPE_MISMATCH_ERROR_CODE

public static final String TYPE_MISMATCH_ERROR_CODE

Error code that a type mismatch error (i.e. a property value not matching the type of the target field) will be registered with: "typeMismatch".

See Also:

TypeMismatchException.ERROR_CODE, Constant Field Values

METHOD_INVOCATION_ERROR_CODE

public static final String METHOD_INVOCATION_ERROR_CODE

Error code that a type mismatch error (i.e. a property value not matching the type of the target field) will be registered with: "methodInvocation".

See Also:

MethodInvocationException.ERROR_CODE, Constant Field Values

logger

protected static final Log logger

We'll create a lot of DataBinder instances: Let's use a static logger.

Constructor Detail

DataBinder

public DataBinder(Object target,
                  String objectName)

Create a new DataBinder instance.

Parameters:

target - target object to bind onto

objectName - name of the target object

Method Detail

createErrors

protected BindException createErrors(Object target,
                                     String objectName)

Create a new Errors instance for this data binder. Can be overridden in subclasses to. Needs to be a subclass of BindException.

Parameters:

target - target object to bind onto

objectName - name of the target object

Returns:

the Errors instance

See Also:

close()

getTarget

public Object getTarget()

Return the wrapped target object.

getObjectName

public String getObjectName()

Return the name of the bound object.

getErrors

public BindException getErrors()

Return the Errors instance for this data binder.

Returns:

the Errors instance, to be treated as Errors or as BindException

See Also:

Errors

getBeanWrapper

protected BeanWrapper getBeanWrapper()

Return the underlying BeanWrapper of the Errors object. To be used by binder subclasses that need bean property checks.

setAllowedFields

public void setAllowedFields(String[] allowedFields)

Register fields that should be allowed for binding. Default is all fields. Restrict this for example to avoid unwanted modifications by malicious users when binding HTTP request parameters.

Supports "xxx*" and "*xxx" patterns. More sophisticated matching can be implemented by overriding the isAllowed method.

Parameters:

allowedFields - array of field names

See Also:

ServletRequestDataBinder, isAllowed(java.lang.String)

getAllowedFields

public String[] getAllowedFields()

Return the fields that should be allowed for binding.

Returns:

array of field names

setRequiredFields

public void setRequiredFields(String[] requiredFields)

Register fields that are required for each binding process.

Parameters:

requiredFields - array of field names

getRequiredFields

public String[] getRequiredFields()

Return the fields that are required for each binding process.

Returns:

array of field names

registerCustomEditor

public void registerCustomEditor(Class requiredType,
                                 PropertyEditor propertyEditor)

Register the given custom property editor for all properties of the given type.

Parameters:

requiredType - type of the property

propertyEditor - editor to register

See Also:

BeanWrapper.registerCustomEditor(java.lang.Class, java.beans.PropertyEditor)

registerCustomEditor

public void registerCustomEditor(Class requiredType,
                                 String field,
                                 PropertyEditor propertyEditor)

Register the given custom property editor for the given type and field, or for all fields of the given type.

If the field denotes an array or Collection, the PropertyEditor will get applied either to the array/Collection itself (the PropertyEditor has to create an array or Collection value) or to each element (the PropertyEditor has to create the element type), depending on the specified required type.

Note: Only one single registered custom editor per property path is supported. In case of a Collection/array, do not register an editor for both the Collection/array and each element on the same property.

Parameters:

requiredType - type of the property (can be null if a field is given but should be specified in any case for consistency checking)

field - name of the field (can also be a nested path), or null if registering an editor for all fields of the given type

propertyEditor - editor to register

See Also:

BeanWrapper.registerCustomEditor(java.lang.Class, java.beans.PropertyEditor)

setMessageCodesResolver

public void setMessageCodesResolver(MessageCodesResolver messageCodesResolver)

Set the strategy to use for resolving errors into message codes. Applies the given strategy to the underlying errors holder.

See Also:

BindException.setMessageCodesResolver(org.springframework.validation.MessageCodesResolver)

bind

public void bind(PropertyValues pvs)

Bind the given property values to this binder's target. This call can create field errors, representing basic binding errors like a required field (code "required"), or type mismatch between value and bean property (code "typeMismatch").

Note that the given PropertyValues should be a throwaway instance: For efficiency, it will be modified to just contain allowed fields if it implements the MutablePropertyValues interface; else, an internal mutable copy will be created for this purpose. Pass in a copy of the PropertyValues if you want your original instance to stay unmodified in any case.

Parameters:

pvs - property values to bind.

isAllowed

protected boolean isAllowed(String field)

Return if the given field is allowed for binding. Invoked for each passed-in property value.

The default implementation checks for "xxx*" and "*xxx" matches. Can be overridden in subclasses.

If the field is found in the allowedFields array as direct match, this method will not be invoked.

Parameters:

field - the field to check

Returns:

if the field is allowed

See Also:

setAllowedFields(java.lang.String[])

getArgumentsForBindingError

protected Object[] getArgumentsForBindingError(String field)

Return FieldError arguments for a binding error on the given field. Invoked for each missing required fields and each type mismatch.

Default implementation returns a DefaultMessageSourceResolvable with "objectName.field" and "field" as codes.

Parameters:

field - the field that caused the binding error

Returns:

the Object array that represents the FieldError arguments

See Also:

DefaultMessageSourceResolvable.getArguments(), DefaultMessageSourceResolvable

close

public Map close()
          throws BindException

Close this DataBinder, which may result in throwing a BindException if it encountered any errors

Returns:

the model Map, containing target object and Errors instance

Throws:

BindException - if there were any errors in the bind operation

See Also:

BindException.getModel()