WebDataBinder (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

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org.springframework.web.bind
Class WebDataBinder

java.lang.Object
  org.springframework.validation.DataBinder
      org.springframework.web.bind.WebDataBinder

All Implemented Interfaces:: PropertyEditorRegistry

Direct Known Subclasses:: PortletRequestDataBinder, ServletRequestDataBinder

public class WebDataBinder
extends DataBinder
extends DataBinder

Special DataBinder for data binding from web request parameters to JavaBean objects. Designed for web environments, but not dependent on the Servlet API; serves as base class for more specific DataBinder variants, such as ServletRequestDataBinder.

Includes support for field markers which address a common problem with HTML checkboxes and select options: detecting that a field was part of the form, but did not generate a request parameter because it was empty. A field marker allows to detect that state and reset the corresponding bean property accordingly.

Since:: 1.2
Author:: Juergen Hoeller
See Also:: DataBinder.registerCustomEditor(java.lang.Class, java.beans.PropertyEditor), DataBinder.setAllowedFields(java.lang.String[]), DataBinder.setRequiredFields(java.lang.String[]), setFieldMarkerPrefix(java.lang.String), ServletRequestDataBinder

Field Summary

static String DEFAULT_FIELD_MARKER_PREFIX
          Default prefix that field marker parameters start with, followed by the field name: e.g.

Fields inherited from class org.springframework.validation.DataBinder

DEFAULT_OBJECT_NAME, logger

Constructor Summary

WebDataBinder(Object target)
          Create a new WebDataBinder instance, with default object name.

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

Method Summary

protected void bindMultipartFiles(Map multipartFiles, MutablePropertyValues mpvs)
          Bind the multipart files contained in the given request, if any (in case of a multipart request).

protected void checkFieldMarkers(MutablePropertyValues mpvs)
          Check the given property values for field markers, i.e. for fields that start with the field marker prefix.

protected void doBind(MutablePropertyValues mpvs)
          This implementation performs a field marker check before delegating to the superclass binding process.

protected Object getEmptyValue(String field, Class fieldType)
          Determine an empty value for the specified field.

String getFieldMarkerPrefix()
          Return the prefix for parameters that mark potentially empty fields.

boolean isBindEmptyMultipartFiles()
          Return whether to bind empty MultipartFile parameters.

void setBindEmptyMultipartFiles(boolean bindEmptyMultipartFiles)
          Set whether to bind empty MultipartFile parameters.

void setFieldMarkerPrefix(String fieldMarkerPrefix)
          Specify a prefix that can be used for parameters that mark potentially empty fields, having "prefix + field" as name.

Methods inherited from class org.springframework.validation.DataBinder

applyPropertyValues, bind, checkAllowedFields, checkRequiredFields, close, findCustomEditor, getAllowedFields, getBindingErrorProcessor, getBindingResult, getDisallowedFields, getErrors, getInternalBindingResult, getObjectName, getPropertyAccessor, getRequiredFields, getTarget, initBeanPropertyAccess, initDirectFieldAccess, isAllowed, isIgnoreInvalidFields, isIgnoreUnknownFields, registerCustomEditor, registerCustomEditor, setAllowedFields, setBindingErrorProcessor, setDisallowedFields, setExtractOldValueForEditor, setIgnoreInvalidFields, setIgnoreUnknownFields, setMessageCodesResolver, setRequiredFields

Methods inherited from class java.lang.Object

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

Field Summary
`static String`	`DEFAULT_FIELD_MARKER_PREFIX` Default prefix that field marker parameters start with, followed by the field name: e.g.

Fields inherited from class org.springframework.validation.DataBinder
`DEFAULT_OBJECT_NAME, logger`

Constructor Summary
`WebDataBinder(Object target)` Create a new WebDataBinder instance, with default object name.
`WebDataBinder(Object target, String objectName)` Create a new WebDataBinder instance.

Method Summary
`protected void`	`bindMultipartFiles(Map multipartFiles, MutablePropertyValues mpvs)` Bind the multipart files contained in the given request, if any (in case of a multipart request).
`protected void`	`checkFieldMarkers(MutablePropertyValues mpvs)` Check the given property values for field markers, i.e. for fields that start with the field marker prefix.
`protected void`	`doBind(MutablePropertyValues mpvs)` This implementation performs a field marker check before delegating to the superclass binding process.
`protected Object`	`getEmptyValue(String field, Class fieldType)` Determine an empty value for the specified field.
`String`	`getFieldMarkerPrefix()` Return the prefix for parameters that mark potentially empty fields.
`boolean`	`isBindEmptyMultipartFiles()` Return whether to bind empty MultipartFile parameters.
`void`	`setBindEmptyMultipartFiles(boolean bindEmptyMultipartFiles)` Set whether to bind empty MultipartFile parameters.
`void`	`setFieldMarkerPrefix(String fieldMarkerPrefix)` Specify a prefix that can be used for parameters that mark potentially empty fields, having "prefix + field" as name.

Methods inherited from class org.springframework.validation.DataBinder
applyPropertyValues, bind, checkAllowedFields, checkRequiredFields, close, findCustomEditor, getAllowedFields, getBindingErrorProcessor, getBindingResult, getDisallowedFields, getErrors, getInternalBindingResult, getObjectName, getPropertyAccessor, getRequiredFields, getTarget, initBeanPropertyAccess, initDirectFieldAccess, isAllowed, isIgnoreInvalidFields, isIgnoreUnknownFields, registerCustomEditor, registerCustomEditor, setAllowedFields, setBindingErrorProcessor, setDisallowedFields, setExtractOldValueForEditor, setIgnoreInvalidFields, setIgnoreUnknownFields, setMessageCodesResolver, setRequiredFields

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

DEFAULT_FIELD_MARKER_PREFIX

public static final String DEFAULT_FIELD_MARKER_PREFIX

Default prefix that field marker parameters start with, followed by the field name: e.g. "_subscribeToNewsletter" for a field "subscribeToNewsletter".

Such a marker parameter indicates that the field was visible, that is, existed in the form that caused the submission. If no corresponding field value parameter was found, the field will be reset. The value of the field marker parameter does not matter in this case; an arbitrary value can be used. This is particularly useful for HTML checkboxes and select options.

See Also:: setFieldMarkerPrefix(java.lang.String), Constant Field Values

Constructor Detail

WebDataBinder

public WebDataBinder(Object target)

Create a new WebDataBinder instance, with default object name.

Parameters:: target - target object to bind onto
See Also:: DataBinder.DEFAULT_OBJECT_NAME

WebDataBinder

public WebDataBinder(Object target,
                     String objectName)

Create a new WebDataBinder instance.

Parameters:: target - target object to bind onto; objectName - objectName of the target object

Method Detail

setFieldMarkerPrefix

public void setFieldMarkerPrefix(String fieldMarkerPrefix)

Specify a prefix that can be used for parameters that mark potentially empty fields, having "prefix + field" as name. Such a marker parameter is checked by existence: You can send any value for it, for example "visible". This is particularly useful for HTML checkboxes and select options.

Default is "_", for "_FIELD" parameters (e.g. "_subscribeToNewsletter"). Set this to null if you want to turn off the empty field check completely.

HTML checkboxes only send a value when they're checked, so it is not possible to detect that a formerly checked box has just been unchecked, at least not with standard HTML means.

One way to address this is to look for a checkbox parameter value if you know that the checkbox has been visible in the form, resetting the checkbox if no value found. In Spring web MVC, this typically happens in a custom onBind implementation.

This auto-reset mechanism addresses this deficiency, provided that a marker parameter is sent for each checkbox field, like "_subscribeToNewsletter" for a "subscribeToNewsletter" field. As the marker parameter is sent in any case, the data binder can detect an empty field and automatically reset its value.

See Also:: DEFAULT_FIELD_MARKER_PREFIX, BaseCommandController.onBind(javax.servlet.http.HttpServletRequest, java.lang.Object, org.springframework.validation.BindException)

getFieldMarkerPrefix

public String getFieldMarkerPrefix()

Return the prefix for parameters that mark potentially empty fields.

setBindEmptyMultipartFiles

public void setBindEmptyMultipartFiles(boolean bindEmptyMultipartFiles)

Set whether to bind empty MultipartFile parameters. Default is "true".

Turn this off if you want to keep an already bound MultipartFile when the user resubmits the form without choosing a different file. Else, the already bound MultipartFile will be replaced by an empty MultipartFile holder.

See Also:: MultipartFile

isBindEmptyMultipartFiles

public boolean isBindEmptyMultipartFiles()

Return whether to bind empty MultipartFile parameters.

doBind

protected void doBind(MutablePropertyValues mpvs)

This implementation performs a field marker check before delegating to the superclass binding process.

Overrides:: doBind in class DataBinder

Parameters:: mpvs - the property values to bind, as MutablePropertyValues instance
See Also:: checkFieldMarkers(org.springframework.beans.MutablePropertyValues)

checkFieldMarkers

protected void checkFieldMarkers(MutablePropertyValues mpvs)

Check the given property values for field markers, i.e. for fields that start with the field marker prefix.

The existence of a field marker indicates that the specified field existed in the form. If the property values do not contain a corresponding field value, the field will be considered as empty and will be reset appropriately.

Parameters:: mpvs - the property values to be bound (can be modified)
See Also:: getFieldMarkerPrefix(), getEmptyValue(String, Class)

getEmptyValue

protected Object getEmptyValue(String field,
                               Class fieldType)

Determine an empty value for the specified field.

Default implementation returns Boolean.FALSE for boolean fields and an empty array of array types. Else, null is used as default.

Parameters:: field - the name of the field; fieldType - the type of the field
Returns:: the empty value (for most fields: null)

bindMultipartFiles

protected void bindMultipartFiles(Map multipartFiles,
                                  MutablePropertyValues mpvs)

Bind the multipart files contained in the given request, if any (in case of a multipart request).

Multipart files will only be added to the property values if they are not empty or if we're configured to bind empty multipart files too.

Parameters:: multipartFiles - Map of field name String to MultipartFile object; mpvs - the property values to be bound (can be modified)
See Also:: MultipartFile, setBindEmptyMultipartFiles(boolean)

Overview

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Deprecated

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Help

The Spring Framework

PREV CLASS NEXT CLASS

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SUMMARY: NESTED | FIELD | CONSTR | METHOD

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WebDataBinder (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

org.springframework.web.bind Class WebDataBinder

DEFAULT_FIELD_MARKER_PREFIX

WebDataBinder

WebDataBinder

setFieldMarkerPrefix

getFieldMarkerPrefix

setBindEmptyMultipartFiles

isBindEmptyMultipartFiles

doBind

checkFieldMarkers

getEmptyValue

bindMultipartFiles

org.springframework.web.bind
Class WebDataBinder