org.springframework.web.bind.WebDataBinder Maven / Gradle / Ivy
/*
* Copyright 2002-2023 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
*
* https://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.Collection;
import java.util.List;
import java.util.Map;
import java.util.function.BiFunction;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.core.CollectionFactory;
import org.springframework.lang.Nullable;
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}.
*
* WARNING: Data binding can lead to security issues by exposing
* parts of the object graph that are not meant to be accessed or modified by
* external clients. Therefore, the design and use of data binding should be considered
* carefully with regard to security. For more details, please refer to the dedicated
* sections on data binding for
* Spring Web MVC and
* Spring WebFlux
* in the reference manual.
*
*
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. Default values, for parameters that are otherwise
* not present, can specify a value for the field other than empty.
*
* @author Juergen Hoeller
* @author Scott Andrews
* @author Brian Clozel
* @since 1.2
* @see #registerCustomEditor
* @see #setAllowedFields
* @see #setRequiredFields
* @see #setFieldMarkerPrefix
* @see #setFieldDefaultPrefix
* @see ServletRequestDataBinder
*/
public class WebDataBinder extends DataBinder {
/**
* Default prefix that field marker parameters start with, followed by the field
* name: for example, "_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 = "_";
/**
* Default prefix that field default parameters start with, followed by the field
* name: for example, "!subscribeToNewsletter" for a field "subscribeToNewsletter".
*
Default parameters differ from field markers in that they provide a default
* value instead of an empty value.
* @see #setFieldDefaultPrefix
*/
public static final String DEFAULT_FIELD_DEFAULT_PREFIX = "!";
@Nullable
private String fieldMarkerPrefix = DEFAULT_FIELD_MARKER_PREFIX;
@Nullable
private String fieldDefaultPrefix = DEFAULT_FIELD_DEFAULT_PREFIX;
private boolean bindEmptyMultipartFiles = true;
/**
* Create a new WebDataBinder instance, with default object name.
* @param target the target object to bind onto (or {@code null}
* if the binder is just used to convert a plain parameter value)
* @see #DEFAULT_OBJECT_NAME
*/
public WebDataBinder(@Nullable Object target) {
super(target);
}
/**
* Create a new WebDataBinder instance.
* @param target the target object to bind onto (or {@code null}
* if the binder is just used to convert a plain parameter value)
* @param objectName the name of the target object
*/
public WebDataBinder(@Nullable 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 (for example, "_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 {@code 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
*/
public void setFieldMarkerPrefix(@Nullable String fieldMarkerPrefix) {
this.fieldMarkerPrefix = fieldMarkerPrefix;
}
/**
* Return the prefix for parameters that mark potentially empty fields.
*/
@Nullable
public String getFieldMarkerPrefix() {
return this.fieldMarkerPrefix;
}
/**
* Specify a prefix that can be used for parameters that indicate default
* value fields, having "prefix + field" as name. The value of the default
* field is used when the field is not provided.
*
Default is "!", for "!FIELD" parameters (for example, "!subscribeToNewsletter").
* Set this to null if you want to turn off the field defaults 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. A default field is especially
* useful when a checkbox represents a non-boolean value.
*
The presence of a default parameter preempts the behavior of a field
* marker for the given field.
* @see #DEFAULT_FIELD_DEFAULT_PREFIX
*/
public void setFieldDefaultPrefix(@Nullable String fieldDefaultPrefix) {
this.fieldDefaultPrefix = fieldDefaultPrefix;
}
/**
* Return the prefix for parameters that mark default fields.
*/
@Nullable
public String getFieldDefaultPrefix() {
return this.fieldDefaultPrefix;
}
/**
* 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;
}
/**
* Check if a value can be resolved if {@link #getFieldDefaultPrefix()}
* or {@link #getFieldMarkerPrefix()} is prepended.
* @param name the name of the value to resolve
* @param type the type of value expected
* @param resolver delegate resolver to use for the checks
* @return the resolved value, or {@code null}
* @since 6.1
*/
@Nullable
protected Object resolvePrefixValue(String name, Class type, BiFunction, Object> resolver) {
Object value = resolver.apply(name, type);
if (value == null) {
String prefix = getFieldDefaultPrefix();
if (prefix != null) {
value = resolver.apply(prefix + name, type);
}
if (value == null) {
prefix = getFieldMarkerPrefix();
if (prefix != null && resolver.apply(prefix + name, type) != null) {
value = getEmptyValue(type);
}
}
}
return value;
}
/**
* This implementation performs a field default and marker check
* before delegating to the superclass binding process.
* @see #checkFieldDefaults
* @see #checkFieldMarkers
*/
@Override
protected void doBind(MutablePropertyValues mpvs) {
checkFieldDefaults(mpvs);
checkFieldMarkers(mpvs);
adaptEmptyArrayIndices(mpvs);
super.doBind(mpvs);
}
/**
* Check the given property values for field defaults,
* i.e. for fields that start with the field default prefix.
* The existence of a field defaults indicates that the specified
* value should be used if the field is otherwise not present.
* @param mpvs the property values to be bound (can be modified)
* @see #getFieldDefaultPrefix
*/
protected void checkFieldDefaults(MutablePropertyValues mpvs) {
String fieldDefaultPrefix = getFieldDefaultPrefix();
if (fieldDefaultPrefix != null) {
PropertyValue[] pvArray = mpvs.getPropertyValues();
for (PropertyValue pv : pvArray) {
if (pv.getName().startsWith(fieldDefaultPrefix)) {
String field = pv.getName().substring(fieldDefaultPrefix.length());
if (getPropertyAccessor().isWritableProperty(field) && !mpvs.contains(field)) {
mpvs.add(field, pv.getValue());
}
mpvs.removePropertyValue(pv);
}
}
}
}
/**
* 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) {
String fieldMarkerPrefix = getFieldMarkerPrefix();
if (fieldMarkerPrefix != null) {
PropertyValue[] pvArray = mpvs.getPropertyValues();
for (PropertyValue pv : pvArray) {
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.add(field, getEmptyValue(field, fieldType));
}
mpvs.removePropertyValue(pv);
}
}
}
}
/**
* Check for property values with names that end on {@code "[]"}. This is
* used by some clients for array syntax without an explicit index value.
* If such values are found, drop the brackets to adapt to the expected way
* of expressing the same for data binding purposes.
* @param mpvs the property values to be bound (can be modified)
* @since 5.3
*/
protected void adaptEmptyArrayIndices(MutablePropertyValues mpvs) {
for (PropertyValue pv : mpvs.getPropertyValues()) {
String name = pv.getName();
if (name.endsWith("[]")) {
String field = name.substring(0, name.length() - 2);
if (getPropertyAccessor().isWritableProperty(field) && !mpvs.contains(field)) {
mpvs.add(field, pv.getValue());
}
mpvs.removePropertyValue(pv);
}
}
}
/**
* Determine an empty value for the specified field.
*
The default implementation delegates to {@link #getEmptyValue(Class)}
* if the field type is known, otherwise falls back to {@code null}.
* @param field the name of the field
* @param fieldType the type of the field
* @return the empty value (for most fields: {@code null})
*/
@Nullable
protected Object getEmptyValue(String field, @Nullable Class fieldType) {
return (fieldType != null ? getEmptyValue(fieldType) : null);
}
/**
* Determine an empty value for the specified field.
*
The default implementation returns:
*
* - {@code Boolean.FALSE} for boolean fields
*
- an empty array for array types
*
- Collection implementations for Collection types
*
- Map implementations for Map types
*
- else, {@code null} is used as default
*
* @param fieldType the type of the field
* @return the empty value (for most fields: {@code null})
* @since 5.0
*/
@Nullable
public Object getEmptyValue(Class fieldType) {
try {
if (boolean.class == fieldType || Boolean.class == fieldType) {
// Special handling of boolean property.
return Boolean.FALSE;
}
else if (fieldType.isArray()) {
// Special handling of array property.
return Array.newInstance(fieldType.componentType(), 0);
}
else if (Collection.class.isAssignableFrom(fieldType)) {
return CollectionFactory.createCollection(fieldType, 0);
}
else if (Map.class.isAssignableFrom(fieldType)) {
return CollectionFactory.createMap(fieldType, 0);
}
}
catch (IllegalArgumentException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to create default value - falling back to null: " + ex.getMessage());
}
}
// Default value: null.
return null;
}
/**
* Bind all multipart files contained in the given request, if any
* (in case of a multipart request). To be called by subclasses.
* 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 a 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 bindMultipart(Map> multipartFiles, MutablePropertyValues mpvs) {
multipartFiles.forEach((key, values) -> {
if (values.size() == 1) {
MultipartFile value = values.get(0);
if (isBindEmptyMultipartFiles() || !value.isEmpty()) {
mpvs.add(key, value);
}
}
else {
mpvs.add(key, values);
}
});
}
}