class PriceClass {
private int value;
public int Value
{
get { return this.value; }
set { this.value = value; }
}
}
struct PriceStruct
{
private int value;
public int Value
{
get { return this.value; }
set { this.value = value; }
}
}
static void Main(string[] args)
{
PriceClass _priceClass = new PriceClass();
Type type = typeof(PriceClass);
PropertyInfo info = type.GetProperty("Value");
info.SetValue(_priceClass, 32, null);
Console.WriteLine(_priceClass.Value);
PriceStruct _priceStruct = new PriceStruct();
type = typeof(PriceStruct);
info = type.GetProperty("Value");
info.SetValue(_priceStruct, 32, null);
Console.WriteLine(_priceStruct.Value);
Debugger.Break();
}
The first value printed is 32 while the second is 0. No exception thrown
It's because boxing your struct makes a copy of it, so you should box it earlier so you call the getter from the same data that you modified. The following code works:
object _priceStruct = new PriceStruct(); //Box first
type = typeof(PriceStruct);
info = type.GetProperty("Value");
info.SetValue(_priceStruct, 32, null);
Console.WriteLine(((PriceStruct)_priceStruct).Value); //now unbox and get value
Debugger.Break();
structs are ValueTypes, which are passed by value, that means you only pass around copies of the entire struct, not a reference to the original object.
So when you pass it into info.SetValue(_priceStruct, 32, null), a copy is passed to the method and mutated, so the original object doesn't get changed at all. Another reason why mutable structs are evil.
You can still change them using reflection but it is a bit long winded.
See this example: http://social.msdn.microsoft.com/Forums/en/netfxbcl/thread/2dd4315c-0d0d-405c-8d52-b4b176997472
Related
New to WebFlux, reactive, and handlers. I've got things "working", but am not understanding why following code is returning "okay" with empty body, vice "not found".
Clarification: The issue-of-concern is in the final return statement of DemoPOJOHandler.getById(). The "short-circuit" code works as expected (i.e., returns "Bad Request" status), but the "switchIfEmpty" path of the final return statement does not appear to get exercised if a DemoPOJORepo.getById(int) returns Mono.empty().
(Note: I've hacked up a list-based "repo" to avoid dealing with database while figuring out handlers and http return types.)
Router implementation ("/v1" is a set of annotation based RESTful endpoints)...
#Configuration
public class DemoPOJORouter {
#Bean
public RouterFunction<ServerResponse> route(DemoPOJOHandler requestHandler) {
return nest(path("/v2"),
nest(accept(APPLICATION_JSON),
RouterFunctions.route(RequestPredicates.GET("/DemoPOJO"), requestHandler::getAll)
.andRoute(RequestPredicates.GET("/DemoPOJO/{id}"), requestHandler::getById)
.andRoute(RequestPredicates.POST("/DemoPOJO"), requestHandler::add)));
}
}
Handler implementation has been "stripped down" to only the code in question. I have a feeling that much of the style is "still imperative", but I've attempted to put the reactive stuff where it "makes the most sense".
If I supply a bad value on the URI (i.e., "foo"), then I get the http "bad request" returned. But, never seem to get the "not found" that should be generated by "switchIfEmpty" if a validly formatted int value is supplied, but it does not map to an entry in the repo.
#Component
public class DemoPOJOHandler {
public static final String PATH_VAR_ID = "id";
private DemoPOJORepo repo = null;
public Mono<ServerResponse> getById(ServerRequest request) {
Mono<DemoPOJO> monoDemoPOJO = null;
Map<String, String> pathVariables = request.pathVariables();
int id = -1;
checkRepoRef(); // part of the list hack
// short-circuit if request doesn't contain id (should never happen)
if ((pathVariables == null)
|| (!pathVariables.containsKey(PATH_VAR_ID))) {
return ServerResponse.badRequest().build();
}
// short-circuit if bad id value
try {
id = Integer.parseInt(pathVariables.get(PATH_VAR_ID));
} catch(NumberFormatException e) {
return ServerResponse.badRequest().build();
}
// get entity by keyValue
monoDemoPOJO = repo.getById(id);
return monoDemoPOJO
.flatMap(demoPOJO -> ServerResponse.ok()
.contentType(MediaType.APPLICATION_JSON)
.syncBody(demoPOJO)
.switchIfEmpty(ServerResponse.notFound().build()));
}
}
Hack of a list-based repo to avoid dealing with data/APIs while working on handlers and http return types.
// local hack to avoid a database for testing
public class DemoPOJORepo {
private static DemoPOJORepo fpRepo = null;
private static int NUM_ROWS = 100;
private Map<Integer, DemoPOJO> fooPOJOMap;
private DemoPOJORepo() {
initMap();
}
public static DemoPOJORepo getInstance() {
if (fpRepo == null) {
fpRepo = new DemoPOJORepo();
}
return fpRepo;
}
public Mono<DemoPOJO> getById(int id) {
Mono<DemoPOJO> monoDP;
if (fooPOJOMap.containsKey(id)) {
monoDP = Mono.just(fooPOJOMap.get(id));
} else {
monoDP = Mono.empty();
}
return monoDP;
}
private Mono<Void> initMap() {
fooPOJOMap = new TreeMap<Integer, DemoPOJO>();
int offset = -1;
for(int ndx=0; ndx<NUM_ROWS; ndx++) {
offset = ndx + 1;
fooPOJOMap.put(offset, new DemoPOJO(offset, "foo_" + offset, offset+100));
}
return Mono.empty();
}
}
Your brackets are in the wrong place causing the swithIfEmpy to apply to the ServerResponse.ok() publisher not the monoDemoPOJO, replace the return with this and it should work:
return monoDemoPOJO
.flatMap(demoPOJO -> ServerResponse.ok().contentType(MediaType.APPLICATION_JSON).syncBody(demoPOJO))
.switchIfEmpty(ServerResponse.notFound().build());
As I can see the code is right. The response code is Bad request because you are trying to convert "foo" to Integer, and when it throws an exception you are returning a Bad request response, so I think it works perfectly fine.
If you use an Integer id that is not present in your database then the answer must be a not found response
I wanted to program a TableBrowser for a MYSQl Database in JavaFX.
My first problem is: i dont know which types i get back from the Database.
So i decided to wrap those types with a Wrapper-class.
To show these values on the GUI, i used the TableColumns setCellValueFactory-method, which
needs a value, that implements ObservableValue.
So i tried to implement the ObservableValue-interface.
But when i run the program it doesnt show the right Values.
TableBrowser after connecting to the Database
Has anyone an idea where i did wrong or knows a more recommended way to implement it ?
Here is the Part of the Code from the TableBrowser
/*
* this variable is used to iterate over the tableview's columns.
* It is a class variable, because it is not possible (for some reasons)
* to use a local variable while working with it in the context of Lambda-expressions
*/
int t = 0;
// those two variables are defined in the class Body
private final TableView<Entry> tableview = new TableView<>();
private final ObservableList<Entry> columndata = FXCollections.observableArrayList();
// the following Code is inside the Button's Actionlistener
for(int i = 1; i <= maxcol; i++) // adds a new TableColum for every colum in the DB
{
tableview.getColumns().add(new TableColumn<Entry, String>rsmd.getColumnName(i)));
}
// iterates over the ResultSet
while(rs.next())
{
// this is the dataset i put in my TableView
Entry row = new Entry(maxcol);
// for each Column i add the columnvalue to the current dataset
for(int i = 1; i <= maxcol; i++)
{
int type = rsmd.getColumnType(i);
Object value = rs.getObject(i);
row.setCellValue(i-1, type, value);
}
// adds a new dataset to the ObservableList<Entry>
columndata.add(row);
}
// puts all datasets in the TableView
tableview.setItems(columndata);
// iterates over all Columns
for(t = 0; t < tableview.getColumns().size(); t++)
{
// should set the CellValueFactory for each Column so it shows the data
/*
* I apologise if there a horrible mistake.
* I never worked with Lamda before and just copied it form an example page :)
*/
tableview.getColumns().get(t).setCellValueFactory(celldata -> celldata.getValue().getCellValue(t-1));
}
This is my Entry class, which is an inner Class in TableBrowserclass
/*
* should represent a Dataset.
* Has an array, which holdes every columnvalue as a WrapperType
*/
private class Entry
{
WrapperType<?>[] columns;
private Entry(int columncount)
{
columns = new WrapperType[columncount];
}
private WrapperType<?> getCellValue(int col)
{
return columns[col];
}
private void setCellValue(int col, int type, Object value)
{
columns[col] = MySQLTypeWrapper.getInstance().wrapType(type, value);
}
}
Here is the MySQLTypeWrapper class, which holds the WrapperType as an inner class
public class MySQLTypeWrapper
{
public WrapperType<?> wrapType(int type, Object Value)
{
Class<?> typeclass = toClass(type);
return new WrapperType<>(typeclass.cast(Value));
}
/*
* returns the appropriate class def for every database type
* Expl: VARCHAR returns String.class
*/
private static Class<?> toClass(int type) {...}
/*
* I copied the content of the of the overridden Methods from StringPropertyBase
* as i have clue how to implement ObservableValue
*/
class WrapperType<T> implements ObservableValue<WrapperType<T>>
{
private T value;
private ExpressionHelper<WrapperType<T>> helper = null;
private WrapperType(T value)
{
this.value = value;
}
#Override
public void addListener(InvalidationListener listener)
{
helper = ExpressionHelper.addListener(helper, this, listener);
}
#Override
public void removeListener(InvalidationListener listener)
{
helper = ExpressionHelper.removeListener(helper, listener);
}
#Override
public void addListener(ChangeListener<? super WrapperType<T>> listener)
{
helper = ExpressionHelper.addListener(helper, this, listener);
}
#Override
public void removeListener(ChangeListener<? super WrapperType<T>> listener)
{
helper = ExpressionHelper.removeListener(helper, listener);
}
#Override
public WrapperType<T> getValue()
{
return this;
}
public String toString()
{
return value.toString();
}
}
}
Thanks for your help in advance :)
As mentioned in the comments, your first problem was not using the TableView's Items property.
For the second part - one solution would be to create a helper method along the lines of
private <T> Callback<TableColumn.CellDataFeatures<Entry,T>,ObservableValue<T>> createCellFactory(int columnIndex) {
return celldata -> celldata.getValue().getCellValue(columnIndex);
}
and then change the loop to
// Now t can be a local variable, as it is not directly passed to the lambda.
for(int t = 0; t < tableview.getColumns().size(); t++)
{
// should set the CellValueFactory for each Column so it shows the data
tableview.getColumns().get(t).setCellValueFactory(createCellFactory(t));
}
Note that this time the variable passed to the lambda is a local effectively-final variable and not an instance variable, so the lambda is created with the correct value every time.
One last word of advice - are you sure you need this amount of generality? What I mean is - it is usually better to create a class to directly represent your DB structure with proper getters and setters, then you can use PropertyValueFactory.
I am using JSON.Net to serialize my objects. For eg, if this is my object
Class MainData
{
[JsonProperty("keyValues")]
string val;
}
the data for 'val' is a key value pair string like this key1:value1.
I have a scenario where I should not get the above 'keyValues' name in my final serialized string and instead get a serialized string which looks like this
{
"key1":"value1"
}
Currently with my serializer I am getting this, which is not what I need
{
"keyValues":"key:value1"
}
Can somebody guide me to any documentation/solution to dynamically assign the name of the field instead of using the default variable name/JSONProperty Name defined inside the object?
Thanks a lot in advance.
I've been struggling with this all day, what I've done is used a dictionary object and serialised this
however I had an error message that was "cannot serialise dictionary", should have read the whole message, "cannot serialise dictionary when the key is not a string or object"
this now works for me and gives me a key/value pair
i have the following objects
public class Meal {
public int mealId;
public int value;
public Meal(int MealId, int Value) {
mealId = MealId;
value = Value;
} }
public class Crew
{
public Meal[] AllocatedMeals {
get {
return new Meal[]{
new Meal(1085, 2),
new Meal(1086, 1) }; } }
public int AllocatedMealTotal {
get {
return this.AllocatedMeals.Sum(x => x.value); } }
}
then the following code
Dictionary<string,string> MealsAllocated = crew.AllocatedMeals.ToDictionary(x => x.mealId.ToString(), x => x.value.ToString());
return new JavaScriptSerializer().Serialize(
new {
Allocated = new {
Total = crew.AllocatedMealTotal,
Values = MealsAllocated } )
to get
"Allocated":{"Total":3,"Values":{"1085":"2","1086":"1"}}
I'm building/updating an EntityFramework EntityObject on runtime. I want to set the properties of the entity class, property names and values are coming from another source.
So I'm doing this;
public static EntityCollection<T> UpdateLocaleEntity<T>(EntityCollection<T> entityCollectionToUpdate, params ILocaleControl[] values) where T : EntityObject
{
foreach (var x in entityCollectionToUpdate)
{
Type t = typeof(T);
dynamic localeEntity = x;
string cultureCode = localeEntity.CultureCode;
for (int j = 0; j < values.Length; j++)
{
var value = values[j].GetLocaleValue(cultureCode);
t.GetProperty(values[j].EntityPropertyName).SetValue(localeEntity, value, null);
}
}
return entityCollectionToUpdate;
}
So, how can I get rid of "t.GetProperty(values[j].EntityPropertyName).SetValue(localeEntity, value, null);" part, is there a dynamic way of doing this?
Something like;
dynamicCastedLocaleEntity.GetProperty(values[j].EntityPropertyName) = value;
Thanks.
Long answer coming up.
Reflection is great in many situations, horrible in some but in almost all cases it's slow.
There are at least 4 different ways to set a property in .NET without having to use reflection.
I thought I demonstrate one of them: Using compiled expression trees. Note that the expression building is rather expensive too so that's why it's very important to cache the delegate one builds with it in a dictionary (for instance):
Expression Trees was introduced in .NET35 and is used for many things. Here I use them to build a property setter expression and then compile it into a delegate.
The example demonstrates different timing for the different cases but here are my numbers:
Control case (hard coded): 0.02s
Reflection: 1.78s
Expression Tree: 0.06s
using System;
using System.Linq.Expressions;
namespace DifferentPropertSetterStrategies
{
class TestClass
{
public string XY
{
get;
set;
}
}
class DelegateFactory
{
public static Action<object, object> GenerateSetPropertyActionForControl(
)
{
return (inst, val) => ((TestClass) inst).XY = (string) val;
}
public static Action<object, object> GenerateSetPropertyActionWithReflection(
Type type,
string property
)
{
var propertyInfo = type.GetProperty(property);
return (inst, val) => propertyInfo.SetValue (inst, val, null);
}
public static Action<object,object> GenerateSetPropertyActionWithLinqExpression (
Type type,
string property
)
{
var propertyInfo = type.GetProperty(property);
var propertyType = propertyInfo.PropertyType;
var instanceParameter = Expression.Parameter(typeof(object), "instance");
var valueParameter = Expression.Parameter(typeof(object), "value");
var lambda = Expression.Lambda<Action<object, object>> (
Expression.Assign (
Expression.Property (Expression.Convert (instanceParameter, type), propertyInfo),
Expression.Convert(valueParameter, propertyType)),
instanceParameter,
valueParameter
);
return lambda.Compile();
}
}
static class Program
{
static void Time (
string tag,
object instance,
object value,
Action<object, object > action
)
{
// Cold run
action(instance, value);
var then = DateTime.Now;
const int Count = 2000000;
for (var iter = 0; iter < Count; ++iter)
{
action (instance, value);
}
var diff = DateTime.Now - then;
Console.WriteLine ("{0} {1} times - {2:0.00}s", tag, Count, diff.TotalSeconds);
}
static void Main(string[] args)
{
var instance = new TestClass ();
var instanceType = instance.GetType ();
const string TestProperty = "XY";
const string TestValue = "Test";
// Control case which just uses a hard coded delegate
Time(
"Control",
instance,
TestValue,
DelegateFactory.GenerateSetPropertyActionForControl ()
);
Time(
"Reflection",
instance,
TestValue,
DelegateFactory.GenerateSetPropertyActionWithReflection (instanceType, TestProperty)
);
Time(
"Expression Trees",
instance,
TestValue,
DelegateFactory.GenerateSetPropertyActionWithLinqExpression(instanceType, TestProperty)
);
Console.ReadKey();
}
}
}
For FuleSnabel's answer, you can speed it up a lot (sometimes twice as fast in my tests). In some tests, it was just as fast as the Control solution:
public static Action<Object,Object> GenerateSetPropertyActionWithLinqExpression2(Type type, String property) {
PropertyInfo pi = type.GetProperty(property,BindingFlags.Instance|BindingFlags.Public);
MethodInfo mi = pi.GetSetMethod();
Type propertyType = pi.PropertyType;
var instance = Expression.Parameter(typeof(Object), "instance");
var value = Expression.Parameter(typeof(Object), "value");
var instance2 = Expression.Convert(instance, type);
var value2 = Expression.Convert(value, pi.PropertyType);
var callExpr = Expression.Call(instance2, mi, value2);
return Expression.Lambda<Action<Object,Object>>(callExpr, instance, value).Compile();
}
possibly not with EntityObject, but if you've had an ExpandoObject than you can do
dynamic entity = new ExpandoObject();
(entity as IDictionary<String, Object>)[values[j].EntityPropertyName] = value
The open source framework ImpromptuInterface has methods to invoke based on a string using the DLR rather than reflection and runs faster than reflection too.
Impromptu.InvokeSet(localeEntity, values[j].EntityPropertyName,value);
I'm afraid not. Any use of a dynamic object is baked-in at compile time. Any call which could vary at run-time has to be done using reflection.
I've got two classes.
public class Class1 {
public string value {get;set;}
}
public class Class2 {
public Class1 myClass1Object {get;set;}
}
I've got an object of type Class2. I need to use reflection on Class2 to set the value property... i.e, if I were doing it without reflection, this is how I would go about it:
Class2 myObject = new Class2();
myObject.myClass1Object.value = "some value";
Is there a way to do the above, while using reflection to access the property "myClass1Object.value" ?
Thanks in advance.
Basically split it into two property accesses. First you get the myClass1Object property, then you set the value property on the result.
Obviously you'll need to take whatever format you've got the property name in and split it out - e.g. by dots. For example, this should do an arbitrary depth of properties:
public void SetProperty(object source, string property, object target)
{
string[] bits = property.Split('.');
for (int i=0; i < bits.Length - 1; i++)
{
PropertyInfo prop = source.GetType().GetProperty(bits[i]);
source = prop.GetValue(source, null);
}
PropertyInfo propertyToSet = source.GetType()
.GetProperty(bits[bits.Length-1]);
propertyToSet.SetValue(source, target, null);
}
Admittedly you'll probably want a bit more error checking than that :)
I was looking for answers to the case where to Get a property value, when the property name is given, but the nesting level of the property is not known.
Eg. if the input is "value" instead of providing a fully qualified property name like "myClass1Object.value".
Your answers inspired my recursive solution below:
public static object GetPropertyValue(object source, string property)
{
PropertyInfo prop = source.GetType().GetProperty(property);
if(prop == null)
{
foreach(PropertyInfo propertyMember in source.GetType().GetProperties())
{
object newSource = propertyMember.GetValue(source, null);
return GetPropertyValue(newSource, property);
}
}
else
{
return prop.GetValue(source,null);
}
return null;
}
public static object GetNestedPropertyValue(object source, string property)
{
PropertyInfo prop = null;
string[] props = property.Split('.');
for (int i = 0; i < props.Length; i++)
{
prop = source.GetType().GetProperty(props[i]);
source = prop.GetValue(source, null);
}
return source;
}