Related
Suppose a JSON column called blob in a MySQL 5.7 database table called "Thing" with the following content:
[
{
"id": 1,
"value": "blue"
},
{
"id": 2,
"value": "red"
}
]
Is it possible to select all records from Thing where the blob contains an object within the array where the id is some dynamic value and the value is also some dynamic value.
E.g. "give me all Things where the blob contains an object whose id is 2 and value is 'red'"
Not sure how to form the WHERE clause below:
SET #id = 2;
SET #value1 = 'red';
SET #value2 = 'blue';
-- with equals?
SELECT *
FROM Thing
WHERE JSON_EXTRACT(blob, '$[*].id ... equals #id ... and .value') = #value1;
-- with an IN clause?
SELECT *
FROM Thing
WHERE JSON_EXTRACT(blob, '$[*].id ... equals #id ... and .value') IN (#value1, #value2);
They said it couldn't be done. They told me I was a fool. Lo and behold, I have done it!
Here are some helper functions to teach Hibernate how to perform JSON functions against a MySQL 5.7 backend, and an example use case. It's confusing, for sure, but it works.
Context
This contrived example is of a Person entity which can have many BioDetails, which is a question/answer type (but is more involved than that). The example within below essentially is searching within two JSON payloads, grabbing JSON values from one to build JSON paths within which to search in the other. In the end, you can pass in a complex structure of AND'd or OR'd criteria, which will be applied against a JSON blob and return only the resulting rows which match.
E.g. give my all Person entities where their age is > 30 and their favorite color is blue or orange. Given that those key/value pairs are stored in a JSON blob, you can find those matched using the example code below.
JSON-search classes and example repo
Classes below use Lombok for brevity.
Classes to allow specification of search criteria
SearchCriteriaContainer
#Data
#EqualsAndHashCode
public class SearchCriteriaContainer
{
private List<SearchCriterion> criteria;
private boolean and;
}
SearchCriterion
#Data
#EqualsAndHashCode(callSuper = true)
public class SearchCriterion extends SearchCriteriaContainer
{
private String field;
private List<String> values;
private SearchOperator operator;
private boolean not = false;
}
SearchOperator
#RequiredArgsConstructor
public enum SearchOperator
{
EQUAL("="),
LESS_THAN("<"),
LESS_THAN_OR_EQUAL("<="),
GREATER_THAN(">"),
GREATER_THAN_OR_EQUAL(">="),
LIKE("like"),
IN("in"),
IS_NULL("is null");
private final String value;
#JsonCreator
public static SearchOperator fromValue(#NotBlank String value)
{
return Stream
.of(SearchOperator.values())
.filter(o -> o.getValue().equals(value))
.findFirst()
.orElseThrow(() ->
{
String message = String.format("Could not find %s with value: %s", SearchOperator.class.getName(), value);
return new IllegalArgumentException(message);
});
}
#JsonValue
public String getValue()
{
return this.value;
}
#Override
public String toString()
{
return value;
}
}
Helper class which is used to call JSON functions
#RequiredArgsConstructor
public class CriteriaBuilderHelper
{
private final CriteriaBuilder criteriaBuilder;
public Expression<String> concat(Expression<?>... values)
{
return criteriaBuilder.function("CONCAT", String.class, values);
}
public Expression<String> substringIndex(Expression<?> value, String delimiter, int count)
{
return substringIndex(value, criteriaBuilder.literal(delimiter), criteriaBuilder.literal(count));
}
public Expression<String> substringIndex(Expression<?> value, Expression<String> delimiter, Expression<Integer> count)
{
return criteriaBuilder.function("SUBSTRING_INDEX", String.class, value, delimiter, count);
}
public Expression<String> jsonUnquote(Expression<?> jsonValue)
{
return criteriaBuilder.function("JSON_UNQUOTE", String.class, jsonValue);
}
public Expression<String> jsonExtract(Expression<?> jsonDoc, Expression<?> path)
{
return criteriaBuilder.function("JSON_EXTRACT", String.class, jsonDoc, path);
}
public Expression<String> jsonSearchOne(Expression<?> jsonDoc, Expression<?> value, Expression<?>... paths)
{
return jsonSearch(jsonDoc, "one", value, paths);
}
public Expression<String> jsonSearch(Expression<?> jsonDoc, Expression<?> value, Expression<?>... paths)
{
return jsonSearch(jsonDoc, "all", value, paths);
}
public Expression<String> jsonSearch(Expression<?> jsonDoc, String oneOrAll, Expression<?> value, Expression<?>... paths)
{
if (!"one".equals(oneOrAll) && !"all".equals(oneOrAll))
{
throw new RuntimeException("Parameter 'oneOrAll' must be 'one' or 'all', not: " + oneOrAll);
}
else
{
final var expressions = new ArrayList<>(List.of(
jsonDoc,
criteriaBuilder.literal(oneOrAll),
value,
criteriaBuilder.nullLiteral(String.class)));
if (paths != null)
{
expressions.addAll(Arrays.asList(paths));
}
return criteriaBuilder.function("JSON_SEARCH", String.class, expressions.toArray(Expression[]::new));
}
}
}
Utility to turn SearchCriteria into MySQL JSON function calls
SearchHelper
public class SearchHelper
{
private static final Pattern pathSeparatorPattern = Pattern.compile("\\.");
public static String getKeyPart(String key)
{
return pathSeparatorPattern.split(key)[0];
}
public static String getPathPart(String key)
{
final var parts = pathSeparatorPattern.split(key);
final var path = new StringBuilder();
for (var i = 1; i < parts.length; i++)
{
if (i > 1)
{
path.append(".");
}
path.append(parts[i]);
}
return path.toString();
}
public static Optional<Predicate> getCriteriaPredicate(SearchCriteriaContainer container, CriteriaBuilder cb, Path<String> bioDetailJson, Path<String> personJson)
{
final var predicates = new ArrayList<Predicate>();
if (container != null && container.getCriteria() != null && container.getCriteria().size() > 0)
{
final var h = new CriteriaBuilderHelper(cb);
container.getCriteria().forEach(ac ->
{
final var groupingOnly = ac.getField() == null && ac.getOperator() == null;
// a criterion can be used for grouping other criterion, and might not have a field/operator/value
if (!groupingOnly)
{
final var key = getKeyPart(ac.getField());
final var path = getPathPart(ac.getField());
final var bioDetailQuestionKeyPathEx = h.jsonUnquote(h.jsonSearchOne(bioDetailJson, cb.literal(key), cb.literal("$[*].key")));
final var bioDetailQuestionIdPathEx = h.concat(h.substringIndex(bioDetailQuestionKeyPathEx, ".", 1), cb.literal(".id"));
final var questionIdEx = h.jsonUnquote(h.jsonExtract(bioDetailJson, bioDetailQuestionIdPathEx));
final var answerPathEx = h.substringIndex(h.jsonUnquote(h.jsonSearchOne(personJson, questionIdEx, cb.literal("$[*].questionId"))), ".", 1);
final var answerValuePathEx = h.concat(answerPathEx, cb.literal("." + path));
final var answerValueEx = h.jsonUnquote(h.jsonExtract(personJson, answerValuePathEx));
switch (ac.getOperator())
{
case IN:
{
final var inEx = cb.in(answerValueEx);
if (ac.getValues() == null || ac.getValues().size() == 0)
{
throw new RuntimeException("No values provided for 'IN' criteria for field: " + ac.getField());
}
else
{
ac.getValues().forEach(inEx::value);
}
predicates.add(inEx);
break;
}
case IS_NULL:
{
predicates.add(cb.isNull(answerValueEx));
break;
}
default:
{
if (ac.getValues() == null || ac.getValues().size() == 0)
{
throw new RuntimeException("No values provided for '" + ac.getOperator() + "' criteria for field: " + ac.getField());
}
else
{
ac.getValues().forEach(value ->
{
final var valueEx = cb.literal(value);
switch (ac.getOperator())
{
case EQUAL:
{
predicates.add(cb.equal(answerValueEx, valueEx));
break;
}
case LESS_THAN:
{
predicates.add(cb.lessThan(answerValueEx, valueEx));
break;
}
case LESS_THAN_OR_EQUAL:
{
predicates.add(cb.lessThanOrEqualTo(answerValueEx, valueEx));
break;
}
case GREATER_THAN:
{
predicates.add(cb.greaterThan(answerValueEx, valueEx));
break;
}
case GREATER_THAN_OR_EQUAL:
{
predicates.add(cb.greaterThanOrEqualTo(answerValueEx, valueEx));
break;
}
case LIKE:
{
predicates.add(cb.like(answerValueEx, valueEx));
break;
}
default:
throw new RuntimeException("Unsupported operator during snapshot search: " + ac.getOperator());
}
});
}
}
}
}
// iterate nested criteria
getAnswerCriteriaPredicate(ac, cb, bioDetailJson, personJson).ifPresent(predicates::add);
});
return Optional.of(container.isAnd()
? cb.and(predicates.toArray(Predicate[]::new))
: cb.or(predicates.toArray(Predicate[]::new)));
}
else
{
return Optional.empty();
}
}
}
Example JPA Specification repository / search method
ExampleRepository
#Repository
public interface PersonRepository extends JpaSpecificationExecutor<Person>
{
default Page<Person> search(PersonSearchDirective directive, Pageable pageable)
{
return findAll((person, query, cb) ->
{
final var bioDetail = person.join(Person_.bioDetail);
final var bioDetailJson = bioDetail.get(BioDetailEntity_.bioDetailJson);
final var personJson = person.get(Person_.personJson);
final var predicates = new ArrayList<>();
SearchHelper
.getCriteriaPredicate(directive.getSearchCriteria(), cb, bioDetailJson, personJson)
.ifPresent(predicates::add);
return cb.and(predicates.toArray(Predicate[]::new));
}, pageable);
}
}
I have a controller action Export which accepts a List of models like below. This is sending back and manipulated dataset back from the view where the user could interact with it. So we have been able to send the data down with much more information.
[HttpPost]
public JsonResult Export(List<MappingExportModel> sources){}
This works fine in all cases but there is one where we have a bigger than normal dataset. This is causing an issue with the export. So far I have tried just passing the values as an object or string but I am unable to convert them into any usable instance after the data is into the controller.
Is it possible to preemptively increase this maxjsonlength value somewhere. The value from the web.config is being ignored from what I have come across so far.
The error I receive is
"Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property"
I need to be able to accept this directly from the ajax request into the controller action. Spinning up a version of JsonResult and then setting the max value will not work because the error is thrown the the data is trying to be deserialized into the object var presented above. We get the value in the original GET request and do set the value before the view is loaded. Now we are taking the data from this view and sending it back plus all the manipulations the users have created.
User posts data to server, the controller action is hit with the data. The error is encountered and spit back out to the browser which handles the error.
You can use custom json length. add the following file in your project and edit your global.asax.cs
Global.asax
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
///// **********
JsonValueProviderFactory jsonValueProviderFactory = null;
foreach (var factory in ValueProviderFactories.Factories)
{
if (factory is JsonValueProviderFactory)
{
jsonValueProviderFactory = factory as JsonValueProviderFactory;
}
}
//remove the default JsonVAlueProviderFactory
if (jsonValueProviderFactory != null) ValueProviderFactories.Factories.Remove(jsonValueProviderFactory);
//add the custom one
ValueProviderFactories.Factories.Add(new CustomJsonValueProviderFactory());
/////*************
}
}
///******** for json length
public sealed class CustomJsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
JsonValueProviderFactory.cs
public sealed class JsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
by this you can pass lengthy json through ajax to controller and if you want to retrieve a lengthy string back to ajax result from controller then add below code in your controller also
//add this for getting large json string
protected override JsonResult Json(object data, string contentType, System.Text.Encoding contentEncoding, JsonRequestBehavior behavior)
{
return new JsonResult()
{
Data = data,
ContentType = contentType,
ContentEncoding = contentEncoding,
JsonRequestBehavior = behavior,
MaxJsonLength = Int32.MaxValue
};
}
I have a list of check boxes that when selected the getEventName method should reurn the key that matches the label. For example if the label is "NEW", the key should be returned when map[key] = "new". These have been defined in the LABEL_EVENTTYPE function below. It is always returning an empty string and can't seem to figure out why.
public static const LABEL_EVENTTYPE_MAP:Object = {
"CANCEL":["cancelled","expired", "doneForDay"],
"NEW":["new"],
"TRADE":["trade"],
"AMEND":["replaced"],
}
private function getEventName(label:String):String{
var map:Object = ReplayConstants.LABEL_EVENTTYPE_MAP;
for each(var key:String in map){
if (map[key] == label){
return key;
}
}
return "";
}
Iterating through object properties requires for..in loop instead of for each.. in
for (var key:String in map){
if (map[key] == label){
return key;
}
}
Also take into account, that objects in your map are arrays, that's why your comparison map[key] == label will always return false.
I have a situation in which I have a very large C# object, however, I only need to return a handful of properties (which can be on nested objects), allow for client-side JavaScript to modify those properties and then send the resulting object back to the server in order to perform in-place partial de-serialization.
The idea is to re-use some very large existing business objects, but be intelligent about only serializing and sending only those properties back to the client application for modification (to keep the amount of data transferred at a minimum).
I basically have an XML file where I pre-define all of the bindings using a "path syntax" which would indicate only those properties I need to serialize. So, I could use something like "WorkOrder.UserField1" or "WorkOrder.Client.Name".
I have tried using a custom contract resolver to determine whether or not a property should be serialized; however, it doesn't seem that I have information as to the "path" (in other words, other properties in the object model up the chain) in order to determine if the property should or should not be serialized.
I have also tried using a custom JsonTextWriter, but it doesn't seem that I can override the methods necessary to keep track of the path, even though there is a Path property available. Is there something perhaps simple that I am overlooking in order to be able to view the path hierarchy of a property being serialized and determine if it should be serialized by looking up the path in a table and making the decision?
The basic difficulty here is that Json.NET is a contract-based serializer which creates a contract for each type to be serialized, then (de)serializes according to the contract. If a type appears in multiple locations in the object hierarchy, the same contract applies. But you want to selectively include properties for a given type depending on its location in the hierarchy, which conflicts with the basic "one type one contract" design.
One quick way to work around this is to serialize to a JObject, then use JToken.SelectTokens() to select only the JSON data you want to return, removing everything else. Since SelectTokens has full support for JSONPath query syntax, you can selectively include using array and property wildcards or other filters, for instance:
"$.FirstLevel[*].Bar"
includes all properties named "Bar" in all array members of a property named "FirstLevel" of the root object.
This should reduce your network usage as desired, but won't save any processing time on the server.
Removal can be accomplished with the following extension methods:
public static partial class JsonExtensions
{
public static TJToken RemoveAllExcept<TJToken>(this TJToken obj, IEnumerable<string> paths) where TJToken : JToken
{
if (obj == null || paths == null)
throw new NullReferenceException();
var keepers = new HashSet<JToken>(paths.SelectMany(path => obj.SelectTokens(path)), ObjectReferenceEqualityComparer<JToken>.Default);
var keepersAndParents = new HashSet<JToken>(keepers.SelectMany(t => t.AncestorsAndSelf()), ObjectReferenceEqualityComparer<JToken>.Default);
// Keep any token that is a keeper, or a child of a keeper, or a parent of a keeper
// I.e. if you have a path ""$.A.B" and it turns out that B is an object, then everything
// under B should be kept.
foreach (var token in obj.DescendantsAndSelfReversed().Where(t => !keepersAndParents.Contains(t) && !t.AncestorsAndSelf().Any(p => keepers.Contains(p))))
token.RemoveFromLowestPossibleParent();
// Return the object itself for fluent style programming.
return obj;
}
public static string SerializeAndSelectTokens<T>(T root, string[] paths, Formatting formatting = Formatting.None, JsonSerializerSettings settings = null)
{
var obj = JObject.FromObject(root, JsonSerializer.CreateDefault(settings));
obj.RemoveAllExcept(paths);
var json = obj.ToString(formatting);
return json;
}
public static TJToken RemoveFromLowestPossibleParent<TJToken>(this TJToken node) where TJToken : JToken
{
if (node == null)
return null;
JToken toRemove;
var property = node.Parent as JProperty;
if (property != null)
{
// Also detach the node from its immediate containing property -- Remove() does not do this even though it seems like it should
toRemove = property;
property.Value = null;
}
else
{
toRemove = node;
}
if (toRemove.Parent != null)
toRemove.Remove();
return node;
}
public static IEnumerable<JToken> DescendantsAndSelfReversed(this JToken node)
{
if (node == null)
throw new ArgumentNullException();
return RecursiveEnumerableExtensions.Traverse(node, t => ListReversed(t as JContainer));
}
// Iterate backwards through a list without throwing an exception if the list is modified.
static IEnumerable<T> ListReversed<T>(this IList<T> list)
{
if (list == null)
yield break;
for (int i = list.Count - 1; i >= 0; i--)
yield return list[i];
}
}
public static partial class RecursiveEnumerableExtensions
{
// Rewritten from the answer by Eric Lippert https://stackoverflow.com/users/88656/eric-lippert
// to "Efficient graph traversal with LINQ - eliminating recursion" http://stackoverflow.com/questions/10253161/efficient-graph-traversal-with-linq-eliminating-recursion
// to ensure items are returned in the order they are encountered.
public static IEnumerable<T> Traverse<T>(
T root,
Func<T, IEnumerable<T>> children)
{
yield return root;
var stack = new Stack<IEnumerator<T>>();
try
{
stack.Push((children(root) ?? Enumerable.Empty<T>()).GetEnumerator());
while (stack.Count != 0)
{
var enumerator = stack.Peek();
if (!enumerator.MoveNext())
{
stack.Pop();
enumerator.Dispose();
}
else
{
yield return enumerator.Current;
stack.Push((children(enumerator.Current) ?? Enumerable.Empty<T>()).GetEnumerator());
}
}
}
finally
{
foreach (var enumerator in stack)
enumerator.Dispose();
}
}
}
/// <summary>
/// A generic object comparerer that would only use object's reference,
/// ignoring any <see cref="IEquatable{T}"/> or <see cref="object.Equals(object)"/> overrides.
/// </summary>
public class ObjectReferenceEqualityComparer<T> : IEqualityComparer<T> where T : class
{
// Adapted from this answer https://stackoverflow.com/a/1890230
// to https://stackoverflow.com/questions/1890058/iequalitycomparert-that-uses-referenceequals
// By https://stackoverflow.com/users/177275/yurik
private static readonly IEqualityComparer<T> _defaultComparer;
static ObjectReferenceEqualityComparer() { _defaultComparer = new ObjectReferenceEqualityComparer<T>(); }
public static IEqualityComparer<T> Default { get { return _defaultComparer; } }
#region IEqualityComparer<T> Members
public bool Equals(T x, T y)
{
return ReferenceEquals(x, y);
}
public int GetHashCode(T obj)
{
return System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(obj);
}
#endregion
}
And then use them like:
public class TestClass
{
public static void Test()
{
var root = new RootObject
{
FirstLevel1 = new FirstLevel
{
SecondLevel1 = new List<SecondLevel> { new SecondLevel { A = "a11", B = "b11", Third1 = new ThirdLevel { Foo = "Foos11", Bar = "Bars11" }, Third2 = new List<ThirdLevel> { new ThirdLevel { Foo = "FooList11", Bar = "BarList11" } } } },
SecondLevel2 = new List<SecondLevel> { new SecondLevel { A = "a12", B = "b12", Third1 = new ThirdLevel { Foo = "Foos12", Bar = "Bars12" }, Third2 = new List<ThirdLevel> { new ThirdLevel { Foo = "FooList12", Bar = "BarList12" } } } },
},
FirstLevel2 = new FirstLevel
{
SecondLevel1 = new List<SecondLevel> { new SecondLevel { A = "a21", B = "b21", Third1 = new ThirdLevel { Foo = "Foos21", Bar = "Bars21" }, Third2 = new List<ThirdLevel> { new ThirdLevel { Foo = "FooList21", Bar = "BarList21" } } } },
SecondLevel2 = new List<SecondLevel> { new SecondLevel { A = "a22", B = "b22", Third1 = new ThirdLevel { Foo = "Foos22", Bar = "Bars22" }, Third2 = new List<ThirdLevel> { new ThirdLevel { Foo = "FooList22", Bar = "BarList22" } } } },
}
};
Assert.IsTrue(JObject.FromObject(root).DescendantsAndSelf().OfType<JValue>().Count() == 24); // No assert
var paths1 = new string[]
{
"$.FirstLevel2.SecondLevel1[*].A",
"$.FirstLevel1.SecondLevel2[*].Third2[*].Bar",
};
Test(root, paths1, 2);
var paths3 = new string[]
{
"$.FirstLevel1.SecondLevel2[*].Third2[*].Bar",
};
Test(root, paths3, 1);
var paths4 = new string[]
{
"$.*.SecondLevel2[*].Third2[*].Bar",
};
Test(root, paths4, 2);
}
static void Test<T>(T root, string [] paths, int expectedCount)
{
var json = JsonExtensions.SerializeAndSelectTokens(root, paths, Formatting.Indented);
Console.WriteLine("Result using paths: {0}", JsonConvert.SerializeObject(paths));
Console.WriteLine(json);
Assert.IsTrue(JObject.Parse(json).DescendantsAndSelf().OfType<JValue>().Count() == expectedCount); // No assert
}
}
public class ThirdLevel
{
public string Foo { get; set; }
public string Bar { get; set; }
}
public class SecondLevel
{
public ThirdLevel Third1 { get; set; }
public List<ThirdLevel> Third2 { get; set; }
public string A { get; set; }
public string B { get; set; }
}
public class FirstLevel
{
public List<SecondLevel> SecondLevel1 { get; set; }
public List<SecondLevel> SecondLevel2 { get; set; }
}
public class RootObject
{
public FirstLevel FirstLevel1 { get; set; }
public FirstLevel FirstLevel2 { get; set; }
}
Note that there is an enhancement request Feature request: ADD JsonProperty.ShouldSerialize(object target, string path) #1857 that would enable this sort of functionality more easily.
Demo fiddles here and here.
The much easier implementation (comparing to the accepted answer) is presented here:
public static class JsonExtensions
{
public static TJToken RemoveAllExcept<TJToken>(this TJToken token, IEnumerable<string> paths) where TJToken : JContainer
{
HashSet<JToken> nodesToRemove = new(ReferenceEqualityComparer.Instance);
HashSet<JToken> nodesToKeep = new(ReferenceEqualityComparer.Instance);
foreach (var whitelistedToken in paths.SelectMany(token.SelectTokens))
TraverseTokenPath(whitelistedToken, nodesToRemove, nodesToKeep);
//In that case neither path from paths has returned any token
if (nodesToKeep.Count == 0)
{
token.RemoveAll();
return token;
}
nodesToRemove.ExceptWith(nodesToKeep);
foreach (var notWhitelistedNode in nodesToRemove)
notWhitelistedNode.Remove();
return token;
}
private static void TraverseTokenPath(JToken value, ISet<JToken> nodesToRemove, ISet<JToken> nodesToKeep)
{
JToken? immediateValue = value;
do
{
nodesToKeep.Add(immediateValue);
if (immediateValue.Parent is JObject or JArray)
{
foreach (var child in immediateValue.Parent.Children())
if (!ReferenceEqualityComparer.Instance.Equals(child, value))
nodesToRemove.Add(child);
}
immediateValue = immediateValue.Parent;
} while (immediateValue != null);
}
}
For most cases this can be achieved by a simple single line extension method
public static string ToJson<T>(this T self, string path) => $#"{{""{path}"":{JObject.FromObject(self)[path]?.ToString(Formatting.None)}}}";
This is only valid for extracting an object nested under the root object but is easily adapted with a separate parameter to specify the output path if needed
Thanks to #dbc answer as a good solution, but like he said, it doesn't affect the performance. Sometimes the data loaded from database has numerous references and only ignoring ReferenceLoopHandling is not enough for serialization; hence the serialized data becomes very large and takes a lot of ram in server, and this is caused by repetition of serializing a single object. In this situation, it's better to make a limited jobject from data straightly, rather than making a jobject and then exclude the unwanted paths from it. This can be done with a little customization of database pure data and a ContractResolver. Let's assume all the database entities inherit from a class or interface like DbModel (this is necessary in this solution). Then by a special ContractResolver, serialization of objects can be limited. A sample is like below:
class TypeName
{
public Type Type { get; set; }
public string Name { get; set; }
}
class MyContractResolver : DefaultContractResolver
{
private List<List<TypeName>> allTypeNames = new List<List<TypeName>>();
public MyContractResolver(Type parentType, string[] includePaths)
{
foreach (var includePath in includePaths)
{
List<TypeName> typeNames = new List<TypeName>() { new TypeName() { Type = parentType } };
var pathChilderen = includePath.Split('.');
for(int i = 0; i < pathChilderen.Length; i++)
{
var propType = typeNames[i].Type.GetProperties().FirstOrDefault(c => c.Name == pathChilderen[i]).PropertyType;
if (propType.GetInterface(nameof(IEnumerable)) != null && propType != typeof(String))
{
propType = propType.GetGenericArguments().Single();
}
typeNames.Add(new TypeName() { Name = pathChilderen[i], Type = propType });
}
allTypeNames.Add(typeNames);
}
}
protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
{
IList<JsonProperty> properties = base.CreateProperties(type, memberSerialization);
// only serializer properties that are in include paths
List<JsonProperty> excludeProperties = new List<JsonProperty>();
foreach (var property in properties)
{
if (typeof(DbModel).IsAssignableFrom(property.PropertyType) || (property.PropertyType.GetInterface(nameof(IEnumerable)) != null && property.PropertyType != typeof(String)))
{
Console.WriteLine(property.PropertyType.ToString());
var exclude = true;
foreach (var typeNames in allTypeNames)
{
var index = typeNames.FindIndex(c => c.Name == property.PropertyName && c.Type == property.PropertyType);
if (index > 0)
{
if (typeNames[index - 1].Type == type)
{
exclude = false;
goto EndSearch;
}
}
}
EndSearch:
if (exclude)
excludeProperties.Add(property);
}
}
properties = properties.Where(c => excludeProperties.All(d => d.PropertyName != c.PropertyName)).ToList();
return properties;
}
}
This class can be used like this:
// return Ok(data);
var jObject = JObject.FromObject(data,
JsonSerializer.CreateDefault(new JsonSerializerSettings()
{
ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
Converters = new List<JsonConverter>()
{
new ValidationProblemDetailsConverter(),
new ProblemDetailsConverter(),
new StringEnumConverter()
},
ContractResolver = new MyContractResolver(typeof(Foo), new[] { "bar", "baz.qux" })
}));
return Ok(jObject);
In this example Foo is the class of main object to return, and bar and baz are properties that are going to be serialized (they are loaded from database too). In addition qux is one of the baz properties that is loaded from database and has to be serialized. In this example all the other properties of each model that are not entities of database (so are not inherited from DbModel) are serialized and all the entities of database that exist in original data but not in the including paths, are ignored to be serialized.
This question already has answers here:
How do you create a dropdownlist from an enum in ASP.NET MVC?
(36 answers)
Closed 8 years ago.
I've been finding all over the place that the common way to bind Enums to DropDowns is through helper methods, which seems a bit overbearing for such a seemingly simple task.
What is the best way to bind Enums to DropDownLists in ASP.Net MVC 4?
You can to this:
#Html.DropDownListFor(model => model.Type, Enum.GetNames(typeof(Rewards.Models.PropertyType)).Select(e => new SelectListItem { Text = e }))
I think it is about the only (clean) way, which is a pity, but at least there are a few options out there. I'd recommend having a look at this blog: http://paulthecyclist.com/2013/05/24/enum-dropdown/
Sorry, it's too long to copy here, but the gist is that he created a new HTML helper method for this.
All the source code is available on GitHub.
Enums are supported by the framework since MVC 5.1:
#Html.EnumDropDownListFor(m => m.Palette)
Displayed text can be customized:
public enum Palette
{
[Display(Name = "Black & White")]
BlackAndWhite,
Colour
}
MSDN link: http://www.asp.net/mvc/overview/releases/mvc51-release-notes#Enum
In my Controller:
var feedTypeList = new Dictionary<short, string>();
foreach (var item in Enum.GetValues(typeof(FeedType)))
{
feedTypeList.Add((short)item, Enum.GetName(typeof(FeedType), item));
}
ViewBag.FeedTypeList = new SelectList(feedTypeList, "Key", "Value", feed.FeedType);
In my View:
#Html.DropDownList("FeedType", (SelectList)ViewBag.FeedTypeList)
The solution from PaulTheCyclist is spot on. But I wouldn't use RESX (I'd have to add a new .resx file for each new enum??)
Here is my HtmlHelper Expression:
public static MvcHtmlString EnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TEnum>> expression, object attributes = null)
{
//Get metadata from enum
var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
var enumType = GetNonNullableModelType(metadata);
var values = Enum.GetValues(enumType).Cast<TEnum>();
//Convert enumeration items into SelectListItems
var items =
from value in values
select new SelectListItem
{
Text = value.ToDescription(),
Value = value.ToString(),
Selected = value.Equals(metadata.Model)
};
//Check for nullable value types
if (metadata.IsNullableValueType)
{
var emptyItem = new List<SelectListItem>
{
new SelectListItem {Text = string.Empty, Value = string.Empty}
};
items = emptyItem.Concat(items);
}
//Return the regular DropDownlist helper
return htmlHelper.DropDownListFor(expression, items, attributes);
}
Here is how I declare my enums:
[Flags]
public enum LoanApplicationType
{
[Description("Undefined")]
Undefined = 0,
[Description("Personal Loan")]
PersonalLoan = 1,
[Description("Mortgage Loan")]
MortgageLoan = 2,
[Description("Vehicle Loan")]
VehicleLoan = 4,
[Description("Small Business")]
SmallBusiness = 8,
}
And here is the call from a Razor View:
<div class="control-group span2">
<div class="controls">
#Html.EnumDropDownListFor(m => m.LoanType, new { #class = "span2" })
</div>
</div>
Where #Model.LoanType is an model property of the LoanApplicationType type
UPDATE: Sorry, forgot to include code for the helper function ToDescription()
/// <summary>
/// Returns Description Attribute information for an Enum value
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static string ToDescription(this Enum value)
{
if (value == null)
{
return string.Empty;
}
var attributes = (DescriptionAttribute[]) value.GetType().GetField(
Convert.ToString(value)).GetCustomAttributes(typeof (DescriptionAttribute), false);
return attributes.Length > 0 ? attributes[0].Description : Convert.ToString(value);
}
Technically, you don't need a helper method, since Html.DropdownListFor only requires a SelectList or Ienumerable<SelectListItem>. You can just turn your enums into such an output and feed it in that way.
I use a static library method to convert enums into List<SelectListItem> with a few params/options:
public static List<SelectListItem> GetEnumsByType<T>(bool useFriendlyName = false, List<T> exclude = null,
List<T> eachSelected = null, bool useIntValue = true) where T : struct, IConvertible
{
var enumList = from enumItem in EnumUtil.GetEnumValuesFor<T>()
where (exclude == null || !exclude.Contains(enumItem))
select enumItem;
var list = new List<SelectListItem>();
foreach (var item in enumList)
{
var selItem = new SelectListItem();
selItem.Text = (useFriendlyName) ? item.ToFriendlyString() : item.ToString();
selItem.Value = (useIntValue) ? item.To<int>().ToString() : item.ToString();
if (eachSelected != null && eachSelected.Contains(item))
selItem.Selected = true;
list.Add(selItem);
}
return list;
}
public static class EnumUtil
{
public static IEnumerable<T> GetEnumValuesFor<T>()
{
return Enum.GetValues(typeof(T)).Cast<T>();
}
// other stuff in here too...
}
/// <summary>
/// Turns Camelcase or underscore separated phrases into properly spaces phrases
/// "DogWithMustard".ToFriendlyString() == "Dog With Mustard"
/// </summary>
public static string ToFriendlyString(this object o)
{
var s = o.ToString();
s = s.Replace("__", " / ").Replace("_", " ");
char[] origArray = s.ToCharArray();
List<char> newCharList = new List<char>();
for (int i = 0; i < origArray.Count(); i++)
{
if (origArray[i].ToString() == origArray[i].ToString().ToUpper())
{
newCharList.Add(' ');
}
newCharList.Add(origArray[i]);
}
s = new string(newCharList.ToArray()).TrimStart();
return s;
}
Your ViewModel can pass in the options you want. Here's a fairly complex one:
public IEnumerable<SelectListItem> PaymentMethodChoices
{
get
{
var exclusions = new List<Membership.Payment.PaymentMethod> { Membership.Payment.PaymentMethod.Unknown, Membership.Payment.PaymentMethod.Reversal };
var selected = new List<Membership.Payment.PaymentMethod> { this.SelectedPaymentMethod };
return GetEnumsByType<Membership.Payment.PaymentMethod>(useFriendlyName: true, exclude: exclusions, eachSelected: selected);
}
}
So you wire your View's DropDownList against that IEnumerable<SelectListItem> property.
Extending the html helper to do it works well, but if you'd like to be able to change the text of the drop down values based on DisplayAttribute mappings, then you would need to modify it similar to this,
(Do this pre MVC 5.1, it's included in 5.1+)
public static IHtmlString EnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> html, Expression<Func<TModel, TEnum>> expression)
{
var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
var enumType = Nullable.GetUnderlyingType(metadata.ModelType) ?? metadata.ModelType;
var enumValues = Enum.GetValues(enumType).Cast<object>();
var items = enumValues.Select(item =>
{
var type = item.GetType();
var member = type.GetMember(item.ToString());
var attribute = member[0].GetCustomAttribute<DisplayAttribute>();
string text = attribute != null ? ((DisplayAttribute)attribute).Name : item.ToString();
string value = ((int)item).ToString();
bool selected = item.Equals(metadata.Model);
return new SelectListItem
{
Text = text,
Value = value,
Selected = selected
};
});
return html.DropDownListFor(expression, items, string.Empty, null);
}