org.springframework.web.bind.WebDataBinder Maven / Gradle / Ivy
/*
* Copyright 2002-2007 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.bind;
import java.lang.reflect.Array;
import java.util.Iterator;
import java.util.Map;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.validation.DataBinder;
import org.springframework.web.multipart.MultipartFile;
/**
* Special {@link 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 {@link org.springframework.web.bind.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.
*
* @author Juergen Hoeller
* @since 1.2
* @see #registerCustomEditor
* @see #setAllowedFields
* @see #setRequiredFields
* @see #setFieldMarkerPrefix
* @see ServletRequestDataBinder
*/
public class WebDataBinder extends DataBinder {
/**
* 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 #setFieldMarkerPrefix
*/
public static final String DEFAULT_FIELD_MARKER_PREFIX = "_";
private String fieldMarkerPrefix = DEFAULT_FIELD_MARKER_PREFIX;
private boolean bindEmptyMultipartFiles = true;
/**
* Create a new WebDataBinder instance, with default object name.
* @param target target object to bind onto
* @see #DEFAULT_OBJECT_NAME
*/
public WebDataBinder(Object target) {
super(target);
}
/**
* Create a new WebDataBinder instance.
* @param target target object to bind onto
* @param objectName objectName of the target object
*/
public WebDataBinder(Object target, String objectName) {
super(target, objectName);
}
/**
* 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 #DEFAULT_FIELD_MARKER_PREFIX
* @see org.springframework.web.servlet.mvc.BaseCommandController#onBind
*/
public void setFieldMarkerPrefix(String fieldMarkerPrefix) {
this.fieldMarkerPrefix = fieldMarkerPrefix;
}
/**
* Return the prefix for parameters that mark potentially empty fields.
*/
public String getFieldMarkerPrefix() {
return this.fieldMarkerPrefix;
}
/**
* 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 org.springframework.web.multipart.MultipartFile
*/
public void setBindEmptyMultipartFiles(boolean bindEmptyMultipartFiles) {
this.bindEmptyMultipartFiles = bindEmptyMultipartFiles;
}
/**
* Return whether to bind empty MultipartFile parameters.
*/
public boolean isBindEmptyMultipartFiles() {
return this.bindEmptyMultipartFiles;
}
/**
* This implementation performs a field marker check
* before delegating to the superclass binding process.
* @see #checkFieldMarkers
*/
protected void doBind(MutablePropertyValues mpvs) {
checkFieldMarkers(mpvs);
super.doBind(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.
* @param mpvs the property values to be bound (can be modified)
* @see #getFieldMarkerPrefix
* @see #getEmptyValue(String, Class)
*/
protected void checkFieldMarkers(MutablePropertyValues mpvs) {
if (getFieldMarkerPrefix() != null) {
String fieldMarkerPrefix = getFieldMarkerPrefix();
PropertyValue[] pvArray = mpvs.getPropertyValues();
for (int i = 0; i < pvArray.length; i++) {
PropertyValue pv = pvArray[i];
if (pv.getName().startsWith(fieldMarkerPrefix)) {
String field = pv.getName().substring(fieldMarkerPrefix.length());
if (getPropertyAccessor().isWritableProperty(field) && !mpvs.contains(field)) {
Class fieldType = getPropertyAccessor().getPropertyType(field);
mpvs.addPropertyValue(field, getEmptyValue(field, fieldType));
}
mpvs.removePropertyValue(pv);
}
}
}
}
/**
* 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.
* @param field the name of the field
* @param fieldType the type of the field
* @return the empty value (for most fields: null)
*/
protected Object getEmptyValue(String field, Class fieldType) {
if (fieldType != null && boolean.class.equals(fieldType) || Boolean.class.equals(fieldType)) {
// Special handling of boolean property.
return Boolean.FALSE;
}
else if (fieldType != null && fieldType.isArray()) {
// Special handling of array property.
return Array.newInstance(fieldType.getComponentType(), 0);
}
else {
// Default value: try null.
return null;
}
}
/**
* 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.
* @param multipartFiles Map of field name String to MultipartFile object
* @param mpvs the property values to be bound (can be modified)
* @see org.springframework.web.multipart.MultipartFile
* @see #setBindEmptyMultipartFiles
*/
protected void bindMultipartFiles(Map multipartFiles, MutablePropertyValues mpvs) {
for (Iterator it = multipartFiles.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
String key = (String) entry.getKey();
MultipartFile value = (MultipartFile) entry.getValue();
if (isBindEmptyMultipartFiles() || !value.isEmpty()) {
mpvs.addPropertyValue(key, value);
}
}
}
}