Support new default values in WebDataBinder

Prior to this commit, binding a `@ModelAttribute` object as a Controller
handler paramater would instantiate the object and set all its
properties, fetching data from the request. When no data is available,
the WebDataBinder tries to bind default "empty" values:
* Boolean.FALSE for boolean types
* empty arrays for array types
* null by default

This commit adds the new default empty values:
* empty Collections for Collection types
* empty Maps for Map types

Rather than using empty implementations provided by `Collections.empty`
(which are not mutable), we're using the closest possible target type
and real implementations, provided by the `CollectionFactory`.

Issue: SPR-13502
This commit is contained in:
Brian Clozel 2016-03-25 21:31:30 +01:00
parent b0c6357540
commit 862d10c128
2 changed files with 64 additions and 18 deletions

View File

@ -1,5 +1,5 @@
/*
* Copyright 2002-2013 the original author or authors.
* Copyright 2002-2016 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.
@ -17,11 +17,13 @@
package org.springframework.web.bind;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.core.CollectionFactory;
import org.springframework.validation.DataBinder;
import org.springframework.web.multipart.MultipartFile;
@ -40,6 +42,7 @@ import org.springframework.web.multipart.MultipartFile;
*
* @author Juergen Hoeller
* @author Scott Andrews
* @author Brian Clozel
* @since 1.2
* @see #registerCustomEditor
* @see #setAllowedFields
@ -243,26 +246,41 @@ public class WebDataBinder extends DataBinder {
/**
* Determine an empty value for the specified field.
* <p>Default implementation returns {@code Boolean.FALSE}
* for boolean fields and an empty array of array types.
* Else, {@code null} is used as default.
* <p>Default implementation returns:
* <ul>
* <li>{@code Boolean.FALSE} for boolean fields
* <li>an empty array for array types
* <li>Collection implementations for Collection types
* <li>Map implementations for Map types
* <li>else, {@code null} is used as default
* </ul>
* @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 == fieldType || Boolean.class == 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;
if (fieldType != null) {
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.getComponentType(), 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 exc) {
return null;
}
}
// Default value: try null.
return null;
}
/**

View File

@ -1,5 +1,5 @@
/*
* Copyright 2002-2015 the original author or authors.
* Copyright 2002-2016 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.
@ -16,10 +16,15 @@
package org.springframework.web.bind.support;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
import java.beans.PropertyEditorSupport;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.junit.Test;
@ -34,8 +39,6 @@ import org.springframework.web.bind.ServletRequestParameterPropertyValues;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.multipart.support.StringMultipartFileEditor;
import static org.junit.Assert.*;
/**
* @author Juergen Hoeller
*/
@ -126,6 +129,31 @@ public class WebRequestDataBinderTests {
assertFalse(target.isPostProcessed());
}
// SPR-13502
@Test
public void testCollectionFieldsDefault() throws Exception {
TestBean target = new TestBean();
target.setSomeSet(null);
target.setSomeList(null);
target.setSomeMap(null);
WebRequestDataBinder binder = new WebRequestDataBinder(target);
MockHttpServletRequest request = new MockHttpServletRequest();
request.addParameter("_someSet", "visible");
request.addParameter("_someList", "visible");
request.addParameter("_someMap", "visible");
binder.bind(new ServletWebRequest(request));
assertThat(target.getSomeSet(), notNullValue());
assertThat(target.getSomeSet(), isA(Set.class));
assertThat(target.getSomeList(), notNullValue());
assertThat(target.getSomeList(), isA(List.class));
assertThat(target.getSomeMap(), notNullValue());
assertThat(target.getSomeMap(), isA(Map.class));
}
@Test
public void testFieldDefaultPreemptsFieldMarker() throws Exception {
TestBean target = new TestBean();