I need an advice for my code. What I want to do is insert a row into a table using Entity Framework Core in ASP.NET Core.
Before inserting new data, I want to check if email and phone number is already used or not.
I want to return specifically, example if return = x, email used. If return = y, phone used.
Here's my code
public int Insert(Employee employee)
{
var checkEmail = context.Employees.Single(e => e.Email == employee.Email);
if (checkEmail != null)
{
var checkPhone = context.Employees.Single(e => e.Phone == employee.Phone);
if (checkPhone != null)
{
context.Employees.Add(employee);
context.SaveChanges();
return 1;
}
return 2;
}
return 3;
}
I'm not sure with my code, is there any advice for the best practice in my case?
I just don't like these "magic numbers" that indicate the result of your checks.... how are you or how is anyone else going to know what 1 or 2 means, 6 months down the road from now??
I would suggest to either at least create a constants class that make it's more obvious what these numbers mean:
public class CheckConstants
{
public const int Successful = 1;
public const int PhoneExists = 2;
public const int EmailExists = 3;
}
and then use these constants in your code:
public int Insert(Employee employee)
{
var checkEmail = context.Employees.Single(e => e.Email == employee.Email);
if (checkEmail != null)
{
var checkPhone = context.Employees.Single(e => e.Phone == employee.Phone);
if (checkPhone != null)
{
context.Employees.Add(employee);
context.SaveChanges();
return CheckConstants.Successful;
}
return CheckConstants.PhoneExists;
}
return CheckConstants.EmailExists;
}
and also in any code that calls this method and need to know about the return status code.
Alternatively, you could also change this to an enum (instead of an int):
public enum CheckConstants
{
Successful, PhoneExists, EmailExists
}
and then just return this enum - instead of an int - from your method:
public CheckConstants Insert(Employee employee)
{
var checkEmail = context.Employees.Single(e => e.Email == employee.Email);
if (checkEmail != null)
{
var checkPhone = context.Employees.Single(e => e.Phone == employee.Phone);
if (checkPhone != null)
{
context.Employees.Add(employee);
context.SaveChanges();
return CheckConstants.Successful;
}
return CheckConstants.PhoneExists;
}
return CheckConstants.EmailExists;
}
merge two database check to one Query
use SingleOrDefault instance of Single
public int Insert(Employee employee)
{
var checkEmail = context.Employees.Select (e=>new {e.Email , e.Phone }).SingleOrDefault(e => e.Email == employee.Email || e.Phone == employee.Phone);
if (checkEmail == null)
{
context.Employees.Add(employee);
context.SaveChanges();
return 1;
}
else if (checkEmail.Email == employee.Email)
return 3;
else
return 2;
}
I am trying to collect 2 data fields from the list object.
I am using Employee object:
public class Employee
{
private long id;
private Source source;
private String name;
private String gender;
// getters
private Builder toBuilder(Builder builder)
{
builder.id = this.summaryDataId;
builder.name = this.name;
builder.gender = this.gender;
builder.source = this.source;
return builder;
}
getting employee data into a list in a service class
final List<Employee> employeeData = employeeDao.retrieveEmployeeData(emp.getID());
and then trying to create a list with employeeId and sourceid (Ex: 1234:3). for this I am trying to use collectors.toList
List<String> employeeCollector = employeeData.stream()
.filter(s -> s.getId != null)
.filter(s -> s.getSource() != null && s.getSource().getId() != null)
.collect(Collectors.toList());
how do i get employeeid:souceid format using collectors.toLis()
You just need an intermediate operation map to extract the employee id and source id
List<String> employeeCollector = employeeData.stream()
.filter(s -> s.getId != null)
.filter(s -> s.getSource() != null && s.getSource().getId() != null)
.map(s-> String.format("%s:%s",s.getId(),s.getSource().getId()))
.collect(Collectors.toList());
I use dart and flutter for mobile app. I use my api to get data from server. But I found a problem, maybe its dart core problem.
I need to add complex queryParams to my URL like
Map<String, Map<String, List<String>>>{"a": {"b": ["c","d"]}, "e": {}}
I use Uri.parse(url).replace(queryParams: myQueryParams).toString()
But Uri.replace() accepts only Map<String, Iterable<String>> and throws an error
Unhandled Exception: type '_InternalLinkedHashMap<String, List<String>>' is not a subtype of type 'Iterable<dynamic>'
I found method which throws this error
static String _makeQuery(String query, int start, int end,
Map<String, dynamic /*String|Iterable<String>*/ > queryParameters) {
if (query != null) {
if (queryParameters != null) {
throw ArgumentError('Both query and queryParameters specified');
}
return _normalizeOrSubstring(query, start, end, _queryCharTable,
escapeDelimiters: true);
}
if (queryParameters == null) return null;
var result = StringBuffer();
var separator = "";
void writeParameter(String key, String value) {
result.write(separator);
separator = "&";
result.write(Uri.encodeQueryComponent(key));
if (value != null && value.isNotEmpty) {
result.write("=");
result.write(Uri.encodeQueryComponent(value));
}
}
queryParameters.forEach((key, value) {
if (value == null || value is String) {
writeParameter(key, value);
} else {
Iterable values = value;
for (String value in values) {
writeParameter(key, value);
}
}
});
return result.toString();
}
So my question is there is some method in dart to add my queryParams to url or I need to create it by my own?
I have modified original method and now its work.
class UrlCreator {
static String addQueryParams(String url, Map<String, dynamic> queryParams) {
var result = StringBuffer();
var separator = "";
void writeParameter(String key, String value) {
result.write(separator);
separator = "&";
result.write(Uri.encodeQueryComponent(key));
if (value != null && value.isNotEmpty) {
result.write("=");
result.write(Uri.encodeQueryComponent(value));
}
}
void buildQuery(Map queryParams, {parentKey}){
queryParams.forEach((key, value){
print("parentKey = $parentKey Key = $key value = $value");
if (value == null || value is String) {
var newKey = parentKey != null ? "$parentKey[$key]" : key;
writeParameter(newKey, value);
} else if (value is Map) {
buildQuery(value, parentKey: key);
} else {
Iterable values = value;
var newKey = parentKey != null ? "$parentKey[$key][]" : "$key[]";
for (String value in values) {
writeParameter(newKey, value);
}
}
});
}
buildQuery(queryParams);
return url + "?" + result.toString();
}
}
I am trying to serialize Guava Range objects to JSON using Gson, however the default serialization fails, and I'm unsure how to correctly implement a TypeAdapter for this generic type.
Gson gson = new Gson();
Range<Integer> range = Range.closed(10, 20);
String json = gson.toJson(range);
System.out.println(json);
Range<Integer> range2 = gson.fromJson(json,
new TypeToken<Range<Integer>>(){}.getType());
System.out.println(range2);
assertEquals(range2, range);
This fails like so:
{"lowerBound":{"endpoint":10},"upperBound":{"endpoint":20}}
PASSED: typeTokenInterface
FAILED: range
java.lang.RuntimeException: Unable to invoke no-args constructor for
com.google.common.collect.Cut<java.lang.Integer>. Register an
InstanceCreator with Gson for this type may fix this problem.
at com.google.gson.internal.ConstructorConstructor$12.construct(
ConstructorConstructor.java:210)
...
Note that the default serialization actually loses information - it fails to report whether the endpoints are open or closed. I would prefer to see it serialized similar to its toString(), e.g. [10‥20] however simply calling toString() won't work with generic Range instances, as the elements of the range may not be primitives (Joda-Time LocalDate instances, for example). For the same reason, implementing a custom TypeAdapter seems difficult, as we don't know how to deserialize the endpoints.
I've implemented most of a TypeAdaptorFactory based on the template provided for Multimap which ought to work, but now I'm stuck on the generics. Here's what I have so far:
public class RangeTypeAdapterFactory implements TypeAdapterFactory {
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
Type type = typeToken.getType();
if (typeToken.getRawType() != Range.class
|| !(type instanceof ParameterizedType)) {
return null;
}
Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
TypeAdapter<?> elementAdapter = (TypeAdapter<?>)gson.getAdapter(TypeToken.get(elementType));
// Bound mismatch: The generic method newRangeAdapter(TypeAdapter<E>) of type
// GsonUtils.RangeTypeAdapterFactory is not applicable for the arguments
// (TypeAdapter<capture#4-of ?>). The inferred type capture#4-of ? is not a valid
// substitute for the bounded parameter <E extends Comparable<?>>
return (TypeAdapter<T>) newRangeAdapter(elementAdapter);
}
private <E extends Comparable<?>> TypeAdapter<Range<E>> newRangeAdapter(final TypeAdapter<E> elementAdapter) {
return new TypeAdapter<Range<E>>() {
#Override
public void write(JsonWriter out, Range<E> value) throws IOException {
if (value == null) {
out.nullValue();
return;
}
String repr = (value.lowerBoundType() == BoundType.CLOSED ? "[" : "(") +
(value.hasLowerBound() ? elementAdapter.toJson(value.lowerEndpoint()) : "-\u221e") +
'\u2025' +
(value.hasLowerBound() ? elementAdapter.toJson(value.upperEndpoint()) : "+\u221e") +
(value.upperBoundType() == BoundType.CLOSED ? "]" : ")");
out.value(repr);
}
public Range<E> read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
String[] endpoints = in.nextString().split("\u2025");
E lower = elementAdapter.fromJson(endpoints[0].substring(1));
E upper = elementAdapter.fromJson(endpoints[1].substring(0,endpoints[1].length()-1));
return Range.range(lower, endpoints[0].charAt(0) == '[' ? BoundType.CLOSED : BoundType.OPEN,
upper, endpoints[1].charAt(endpoints[1].length()-1) == '[' ? BoundType.CLOSED : BoundType.OPEN);
}
};
}
}
However the return (TypeAdapter<T>) newRangeAdapter(elementAdapter); line has a compilation error and I'm now at a loss.
What's the best way to resolve this error? Is there a better way to serialize Range objects that I'm missing? What about if I want to serialize RangeSets?
Rather frustrating that the Google utility library and Google serialization library seem to require so much glue to work together :(
This feels somewhat like reinventing the wheel, but it was a lot quicker to put together and test than the time spent trying to get Gson to behave, so at least presently I'll be using the following Converters to serialize Range and RangeSet*, rather than Gson.
/**
* Converter between Range instances and Strings, essentially a custom serializer.
* Ideally we'd let Gson or Guava do this for us, but presently this is cleaner.
*/
public static <T extends Comparable<? super T>> Converter<Range<T>, String> rangeConverter(final Converter<T, String> elementConverter) {
final String NEG_INFINITY = "-\u221e";
final String POS_INFINITY = "+\u221e";
final String DOTDOT = "\u2025";
return new Converter<Range<T>, String>() {
#Override
protected String doForward(Range<T> range) {
return (range.hasLowerBound() && range.lowerBoundType() == BoundType.CLOSED ? "[" : "(") +
(range.hasLowerBound() ? elementConverter.convert(range.lowerEndpoint()) : NEG_INFINITY) +
DOTDOT +
(range.hasUpperBound() ? elementConverter.convert(range.upperEndpoint()) : POS_INFINITY) +
(range.hasUpperBound() && range.upperBoundType() == BoundType.CLOSED ? "]" : ")");
}
#Override
protected Range<T> doBackward(String range) {
String[] endpoints = range.split(DOTDOT);
Range<T> ret = Range.all();
if(!endpoints[0].substring(1).equals(NEG_INFINITY)) {
T lower = elementConverter.reverse().convert(endpoints[0].substring(1));
ret = ret.intersection(Range.downTo(lower, endpoints[0].charAt(0) == '[' ? BoundType.CLOSED : BoundType.OPEN));
}
if(!endpoints[1].substring(0,endpoints[1].length()-1).equals(POS_INFINITY)) {
T upper = elementConverter.reverse().convert(endpoints[1].substring(0,endpoints[1].length()-1));
ret = ret.intersection(Range.upTo(upper, endpoints[1].charAt(endpoints[1].length()-1) == ']' ? BoundType.CLOSED : BoundType.OPEN));
}
return ret;
}
};
}
/**
* Converter between RangeSet instances and Strings, essentially a custom serializer.
* Ideally we'd let Gson or Guava do this for us, but presently this is cleaner.
*/
public static <T extends Comparable<? super T>> Converter<RangeSet<T>, String> rangeSetConverter(final Converter<T, String> elementConverter) {
return new Converter<RangeSet<T>, String>() {
private final Converter<Range<T>, String> rangeConverter = rangeConverter(elementConverter);
#Override
protected String doForward(RangeSet<T> rs) {
ArrayList<String> ls = new ArrayList<>();
for(Range<T> range : rs.asRanges()) {
ls.add(rangeConverter.convert(range));
}
return Joiner.on(", ").join(ls);
}
#Override
protected RangeSet<T> doBackward(String rs) {
Iterable<String> parts = Splitter.on(",").trimResults().split(rs);
ImmutableRangeSet.Builder<T> build = ImmutableRangeSet.builder();
for(String range : parts) {
build.add(rangeConverter.reverse().convert(range));
}
return build.build();
}
};
}
*For inter-process communication, Java serialization would likely work just fine, as both classes implement Serializable. However I'm serializing to disk for more permanent storage, meaning I need a format I can trust won't change over time. Guava's serialization doesn't provide that guarantee.
Here is a Gson JsonSerializer and JsonDeserializer that generically supports a Range: https://github.com/jamespedwards42/Fava/wiki/Range-Marshaller
#Override
public JsonElement serialize(final Range src, final Type typeOfSrc, final JsonSerializationContext context) {
final JsonObject jsonObject = new JsonObject();
if ( src.hasLowerBound() ) {
jsonObject.add( "lowerBoundType", context.serialize( src.lowerBoundType() ) );
jsonObject.add( "lowerBound", context.serialize( src.lowerEndpoint() ) );
} else
jsonObject.add( "lowerBoundType", context.serialize( BoundType.OPEN ) );
if ( src.hasUpperBound() ) {
jsonObject.add( "upperBoundType", context.serialize( src.upperBoundType() ) );
jsonObject.add( "upperBound", context.serialize( src.upperEndpoint() ) );
} else
jsonObject.add( "upperBoundType", context.serialize( BoundType.OPEN ) );
return jsonObject;
}
#Override
public Range<? extends Comparable<?>> deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context) throws JsonParseException {
if ( !( typeOfT instanceof ParameterizedType ) )
throw new IllegalStateException( "typeOfT must be a parameterized Range." );
final JsonObject jsonObject = json.getAsJsonObject();
final JsonElement lowerBoundTypeJsonElement = jsonObject.get( "lowerBoundType" );
final JsonElement upperBoundTypeJsonElement = jsonObject.get( "upperBoundType" );
if ( lowerBoundTypeJsonElement == null || upperBoundTypeJsonElement == null )
throw new IllegalStateException( "Range " + json
+ "was not serialized with this serializer! The default serialization does not store the boundary types, therfore we can not deserialize." );
final Type type = ( ( ParameterizedType ) typeOfT ).getActualTypeArguments()[0];
final BoundType lowerBoundType = context.deserialize( lowerBoundTypeJsonElement, BoundType.class );
final JsonElement lowerBoundJsonElement = jsonObject.get( "lowerBound" );
final Comparable<?> lowerBound = lowerBoundJsonElement == null ? null : context.deserialize( lowerBoundJsonElement, type );
final BoundType upperBoundType = context.deserialize( upperBoundTypeJsonElement, BoundType.class );
final JsonElement upperBoundJsonElement = jsonObject.get( "upperBound" );
final Comparable<?> upperBound = upperBoundJsonElement == null ? null : context.deserialize( upperBoundJsonElement, type );
if ( lowerBound == null && upperBound != null )
return Range.upTo( upperBound, upperBoundType );
else if ( lowerBound != null && upperBound == null )
return Range.downTo( lowerBound, lowerBoundType );
else if ( lowerBound == null && upperBound == null )
return Range.all();
return Range.range( lowerBound, lowerBoundType, upperBound, upperBoundType );
}
Here is a straight forward solution. Works very well
import com.google.common.collect.BoundType;
import com.google.common.collect.Range;
import com.google.gson.*;
import java.lang.reflect.Type;
public class GoogleRangeAdapter implements JsonSerializer, JsonDeserializer {
public static String TK_hasLowerBound = "hasLowerBound";
public static String TK_hasUpperBound = "hasUpperBound";
public static String TK_lowerBoundType = "lowerBoundType";
public static String TK_upperBoundType = "upperBoundType";
public static String TK_lowerBound = "lowerBound";
public static String TK_upperBound = "upperBound";
#Override
public Object deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
JsonObject jsonObject = (JsonObject)json;
boolean hasLowerBound = jsonObject.get(TK_hasLowerBound).getAsBoolean();
boolean hasUpperBound = jsonObject.get(TK_hasUpperBound).getAsBoolean();
if (!hasLowerBound && !hasUpperBound) {
return Range.all();
}
else if (!hasLowerBound && hasUpperBound){
double upperBound = jsonObject.get(TK_upperBound).getAsDouble();
BoundType upperBoundType = BoundType.valueOf(jsonObject.get(TK_upperBoundType).getAsString());
if (upperBoundType == BoundType.OPEN)
return Range.lessThan(upperBound);
else
return Range.atMost(upperBound);
}
else if (hasLowerBound && !hasUpperBound){
double lowerBound = jsonObject.get(TK_lowerBound).getAsDouble();
BoundType lowerBoundType = BoundType.valueOf(jsonObject.get(TK_lowerBoundType).getAsString());
if (lowerBoundType == BoundType.OPEN)
return Range.greaterThan(lowerBound);
else
return Range.atLeast(lowerBound);
}
else {
double lowerBound = jsonObject.get(TK_lowerBound).getAsDouble();
double upperBound = jsonObject.get(TK_upperBound).getAsDouble();
BoundType upperBoundType = BoundType.valueOf(jsonObject.get(TK_upperBoundType).getAsString());
BoundType lowerBoundType = BoundType.valueOf(jsonObject.get(TK_lowerBoundType).getAsString());
if (lowerBoundType == BoundType.OPEN && upperBoundType == BoundType.OPEN)
return Range.open(lowerBound, upperBound);
else if (lowerBoundType == BoundType.OPEN && upperBoundType == BoundType.CLOSED)
return Range.openClosed(lowerBound, upperBound);
else if (lowerBoundType == BoundType.CLOSED && upperBoundType == BoundType.OPEN)
return Range.closedOpen(lowerBound, upperBound);
else
return Range.closed(lowerBound, upperBound);
}
}
#Override
public JsonElement serialize(Object src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject jsonObject = new JsonObject();
Range<Double> range = (Range<Double>)src;
boolean hasLowerBound = range.hasLowerBound();
boolean hasUpperBound = range.hasUpperBound();
jsonObject.addProperty(TK_hasLowerBound, hasLowerBound);
jsonObject.addProperty(TK_hasUpperBound, hasUpperBound);
if (hasLowerBound) {
jsonObject.addProperty(TK_lowerBound, range.lowerEndpoint());
jsonObject.addProperty(TK_lowerBoundType, range.lowerBoundType().name());
}
if (hasUpperBound) {
jsonObject.addProperty(TK_upperBound, range.upperEndpoint());
jsonObject.addProperty(TK_upperBoundType, range.upperBoundType().name());
}
return jsonObject;
}
}
How to append raw sql e.g. condition to entity framework linq query?
I'm open to all suggestions so it's not mandatory to append it to linq query main point is to e.g. filter by adding some custom sql to query overall.
Using IQueryable we can append the condition on the Linq to entity query.
private IQueryable<Customer> FilterList(IQueryable<Customer> customer, List<string> filter, string filterValue)
{
IQueryable<Customer> query = new List<Customer>().AsQueryable();
if (filter == null || string.IsNullOrEmpty(filterValue))
{
return customer;
}
var filterLower = filter.First().ToLower();
filterValue = filterValue.ToLower();
if (filterLower.Contains("retail") || (filterLower.Contains("distributor"))
{
return customer.Where(x => (!string.IsNullOrEmpty(x.Retail) && x.Retail.Contains(filterValue)) || (!string.IsNullOrEmpty(x.Distributor) && x.Distributor.Contains(filterValue)));
}
if (filterLower.Contains("retail"))
{
query = customer.Where( x=> !string.IsNullOrEmpty(x.Distributor) && x.Distributor.Contains(filterValue));
}
if (filterLower.Contains("distributor"))
{
query = customer.Where(x => !string.IsNullOrEmpty(x.Retail) && x.Retail.Contains(filterValue)).Union(query);
}
return query;
}