How can i Remove this error. pls Help me in this...
Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<Linq.Model.usp_DisplayrecordsResult>' to 'System.Data.Linq.Link<Linq.Model.usp_DisplayrecordsResult>' C:\Users\anu\Documents\Visual Studio 2010\Projects\Linq.DAL\DAL.cs 23 24 Linq.DAL
method in which error raised is as follows..
Linq.Model.DataAccessDataContext _DataAccessDataContext;
public Link<usp_DisplayrecordsResult> DispPersons()
{
try
{
_DataAccessDataContext = new Linq.Model.DataAccessDataContext();
var query = _DataAccessDataContext.usp_Displayrecords();
List<usp_DisplayrecordsResult> Listresult = new List<usp_DisplayrecordsResult>(query);
return Listresult;
}
catch (Exception ex)
{
throw ex;
}
}
I don't think that you intended to use the Link structure as return type. If you change that to List it will compile:
public List<usp_DisplayrecordsResult> DispPersons()
Related
With OpenCSV, how do I append to existing CSV using a MappingStrategy? There are lots of examples I could find where NOT using a Bean mapping stategy BUT I like the dynamic nature of the column mapping with bean strategy and would like to get it working this way. Here is my code, which just rewrites the single line to CSV file instead of appending.
How can I fix this? Using OpenCSV 4.5 . Note: I set my FileWriter for append=true . This scenario is not working as I expected. Re-running this method simply results in over-writing the entire file with a header and a single row.
public void addRowToCSV(PerfMetric rowData) {
File file = new File(PerfTestMetric.CSV_FILE_PATH);
try {
CSVWriter writer = new CSVWriter(new FileWriter(file, true));
CustomCSVMappingStrategy<PerfMetric> mappingStrategy
= new CustomCSVMappingStrategy<>();
mappingStrategy.setType(PerfMetric.class);
StatefulBeanToCsv<PerfMetric> beanToCsv
= new StatefulBeanToCsvBuilder<PerfMetric>(writer)
.withMappingStrategy(mappingStrategy)
.withSeparator(',')
.withApplyQuotesToAll(false)
.build();
try {
beanToCsv.write(rowData);
} catch (CsvDataTypeMismatchException e) {
e.printStackTrace();
} catch (CsvRequiredFieldEmptyException e) {
e.printStackTrace();
}
writer.flush();
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Or, is the usual pattern to load all rows into a List and then re-write entire file? I was able to get it to work by writing two MappingStrategy mapping strategies and then conditionally using them with a if-file-exists but doing it that way leaves me with a "Unchecked assignment" warning in my code. Not ideal; hoping for an elegant solution?
I've updated OpenCSV to version 5.1 and got it working. In my case I needed the CSV headers to have a specific name and position, so I'm using both #CsvBindByName and #CsvBindByPosition, and needed to create a custom MappingStrategy to get it working.
Later, I needed to edit the MappingStrategy to enable appending, so when it's in Appending mode I don't need to generate a CSV header.
public class CustomMappingStrategy<T> extends ColumnPositionMappingStrategy<T> {
private boolean useHeader=true;
public CustomMappingStrategy(){
}
public CustomMappingStrategy(boolean useHeader) {
this.useHeader = useHeader;
}
#Override
public String[] generateHeader(T bean) throws CsvRequiredFieldEmptyException {
final int numColumns = FieldUtils.getAllFields(bean.getClass()).length;
super.setColumnMapping(new String[numColumns]);
if (numColumns == -1) {
return super.generateHeader(bean);
}
String[] header = new String[numColumns];
if(!useHeader){
return ArrayUtils.EMPTY_STRING_ARRAY;
}
BeanField<T, Integer> beanField;
for (int i = 0; i < numColumns; i++){
beanField = findField(i);
String columnHeaderName = extractHeaderName(beanField);
header[i] = columnHeaderName;
}
return header;
}
private String extractHeaderName(final BeanField<T, Integer> beanField){
if (beanField == null || beanField.getField() == null || beanField.getField().getDeclaredAnnotationsByType(CsvBindByName.class).length == 0){
return StringUtils.EMPTY;
}
//return value of CsvBindByName annotation
final CsvBindByName bindByNameAnnotation = beanField.getField().getDeclaredAnnotationsByType(CsvBindByName.class)[0];
return bindByNameAnnotation.column();
}
}
Now if you use the default constructor it'll add the header to the generated CSV, and using a boolean you can tell it to add a header or to ignore it.
I never found an answer to this question and so what I ended up doing was doing a branch if-condition where .csv file exists or not. If file exists I used MappingStrategyWithoutHeader strategy, and if file didn't yet exist, I used MappingStrategyWithHeader strategy. Not ideal, but I got it working.
Hello there I am trying to force a promise to end to get the result from it but it just stucks on loading.
public class CacheController extends Controller {
private AsyncCacheApi cache;
public Result cache()
{
String test = "nice";
cache.set("item.key", test, 15);
Customer user = new Customer("Ana", 12);
CompletionStage<Done> result = cache.set(user.getName(), user);
block(result);
return ok("Cached");
}
public Result checkCache() throws Exception
{
Logger.info("start");
//CompletionStage<String> news = cache.get("item.key");
//news.thenRun(() -> System.out.println("works"));
CompletionStage<Customer> result = cache.get("Ana");
Logger.info("step 1");
Logger.info(cache.get("Ana").toString());
Logger.info("Step 2");
Customer c = block(result);
Logger.info("Step 3 " + c.getName());
//result.thenRun(() -> setUser(result)).thenRun(() -> Logger.info(user.getName() + " " + user.getAge()));
return ok("cancan");
}
private <T> T block(CompletionStage<T> stage) {
try {
return stage.toCompletableFuture().get();
} catch (Throwable e) {
throw new RuntimeException(e);
}
}
}
When trying to load the page it gets stuck after step2 at line 56: Customer c = block(result); by my guesses
Any ideas to fix it?
#Codrin
I had the same problem. But, see https://www.playframework.com/documentation/2.6.x/JavaCache#Setting-the-execution-context
By default, all Ehcache operations are blocking, and async implementations will block threads in the default execution context.
Maybe CompletableFuture.get() gets stuck because it is executed in the same thread with the caller.
Referring to the linked page, I added snippet below to my application.conf and it worked.
play.cache.dispatcher = "contexts.blockingCacheDispatcher"
contexts {
blockingCacheDispatcher {
fork-join-executor {
parallelism-factor = 3.0
}
}
}
I work in Android Studio with libgdx and gdx-sqlite. I want a simple query from my database with the following code.
try {
cursorSettings = dbHandler.rawQuery("SELECT "+COLUMN_SETTING+" FROM "+TABLE_SETTINGS+" WHERE "+COLUMN_SETTINGSID+" =13");
System.out.println(cursorSettings.getLong(0));
} catch (SQLiteGdxException e) {
e.printStackTrace();
}
The Desktop-Version works without problems, but in the android version I get the following error:
05-25 10:21:47.341 11978-12232/ch.shuttering.rapporte E/AndroidRuntime: FATAL EXCEPTION: GLThread 82275
Process: ch.shuttering.rapporte, PID: 11978
android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
at android.database.AbstractCursor.checkPosition(AbstractCursor.java:460)
at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:74)
at com.badlogic.gdx.sqlite.android.AndroidCursor.getLong(AndroidCursor.java:61)
at ch.shuttering.rapporte.Manager.SQLiteManager.SaveMangerSQLite.creatSQLiteSettings(SaveMangerSQLite.java:295)
at ch.shuttering.rapporte.RapporteMain.create(RapporteMain.java:66)
at com.badlogic.gdx.backends.android.AndroidGraphics.onSurfaceChanged(AndroidGraphics.java:311)
at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1546)
at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1262)
So every time I make a getXXX () query from the cursor I get an error, but if I now use the following code:
try {
cursorSettings = dbHandler.rawQuery("SELECT * FROM "+TABLE_SETTINGS);
} catch (SQLiteGdxException e) {
e.printStackTrace();
}
while (cursorSettings.next()) {
Gdx.app.log("FromDb", String.valueOf(cursorSettings.getString(1)));
}
I have a correct output with all data.
Does anyone have an idea what the problem is?
Thank you for your help
Okay I found the problem by myself, that was the code in the Android class
#Override
public long getLong (int columnIndex) {
try {
return cursor.getLong(columnIndex);
} catch (SQLiteException e) {
Gdx.app.log(DatabaseFactory.ERROR_TAG, "There was an error in getting the long", e);
throw new SQLiteGdxRuntimeException(e);
}
}
The problem is that in android the cursor points to -1 so it must first be set to the correct position, the following code solves the problem
#Override
public long getLong (int columnIndex) {
try {
cursor.moveToFirst();
return cursor.getLong(columnIndex);
} catch (SQLiteException e) {
Gdx.app.log(DatabaseFactory.ERROR_TAG, "There was an error in getting the long", e);
throw new SQLiteGdxRuntimeException(e);
}
}
You can found this code in the library gdx-sqlite-android.jar in the class AndroidCursor.
I hope the solution helps someone.
I am implementing a method using Vertx to check the existence of certain value in the database and use Handler with AsyncResult.
I would like to know which one is the best practice:
Option 1: When nothing found, Handler is with succeededFuture but with result as FALSE:
public void checkExistence (..., String itemToFind, Handler<AsyncResult<Boolean>> resultHandler) {
// ....
doQuery(..., queryHandler -> {
if (queryHandler.succeeded()) {
List<JsonObject> results = queryHandler.result();
boolean foundIt = false;
for (JsonObject json: results) {
if (json.getString("someKey").equals(itemToFind)) {
foundIt = true;
break;
}
}
resultHandler.handle(Future.succeededFuture(foundIt));
} else {
resultHandler.handle(Future.failedFuture(queryHandler.cause().toString()));
}
});
}
Option 2: When nothing found, Handler is with failedFuture:
public void checkExistence (..., String itemToFind, Handler<AsyncResult<Void>> resultHandler) {
// ....
doQuery(..., queryHandler -> {
if (queryHandler.succeeded()) {
List<JsonObject> results = queryHandler.result();
boolean foundIt = false;
for (JsonObject json: results) {
if (json.getString("someKey").equals(itemToFind)) {
foundIt = true;
break;
}
}
// HERE IS THE DIFFERENCE!!!
if (foundIt) {
resultHandler.handle(Future.succeededFuture());
} else {
resultHandler.handle(Future.failedFuture("Item " + itemToFind + " not found!"));
}
} else {
resultHandler.handle(Future.failedFuture(queryHandler.cause().toString()));
}
});
}
UPDATE:
Let's say I have another example, instead of checking the existence, I would like to get all the results. Do I check the Empty results? Do I treat Empty as failure or success?
Option 1: only output them when it's not null or empty, otherwise, fail it
public void getItems(..., String itemType, Handler<AsyncResult<List<Item>>> resultHandler) {
// ....
doQuery(..., queryHandler -> {
if (queryHandler.succeeded()) {
List<Item> items = queryHandler.result();
if (items != null && !items.empty()) {
resultHandler.handle(Future.succeededFuture(items));
} else {
resultHandler.handle(Future.failedFuture("No items found!"));
}
} else {
resultHandler.handle(Future.failedFuture(queryHandler.cause().toString()));
}
});
}
Option 2: output results I got, even though it could be empty or null
public void getItems(..., String itemType, Handler<AsyncResult<List<Item>>> resultHandler) {
// ....
doQuery(..., queryHandler -> {
if (queryHandler.succeeded()) {
List<Item> items = queryHandler.result();
resultHandler.handle(Future.succeededFuture(items));
} else {
resultHandler.handle(Future.failedFuture(queryHandler.cause().toString()));
}
});
}
The 1st one option is better, because you can clearly say, that checkExistence returned True or False and completed successfully or it failed with some exception (database issue, etc.).
But lets say, you've decided to stick with 2nd option. Then, imagine you have another method:
void getEntity(int id, Handler<AsyncResult<Entity>> resultHandler);
If entity with provided id doesn't exists, will you throw exception (using Future.failedFuture) or return null (using Future.succeededFuture)? I think, you should throw exception to make your methods logic similar to each other. But again, is that exceptional situation?
For case with returning list of entities you can just return empty list, if there are no entities. Same goes to single entity: it's better to return Optional<Entity> instead of Entity, because in this way you avoid NullPointerException and don't have nullable variables in the code. What's better: Optional<List<Entity>> or empty List<Entity>, it's open question.
Particularly if you're writing this as reusable code, then definitely go with your first option. This method is simply determining whether an item exists, and so should simply return whether it does or not. How is this particular method to know whether it's an error condition that the item doesn't exist?
Some caller might determine that it is indeed an error; it that's the case, then it will throw an appropriate exception if the Future returns with false. But another caller might simply need to know whether the item exists before proceeding; in that case, you'll find yourself using exception handling to compose your business logic.
I 've built an ASP.NET website using EF. I created a DataContext class which implements the singleton pattern. My DAO classes (singletons too) instanciate this datacontext and store it in a property. They use it in order to query the SQLServer DataBase. This worked ok for 3 months but I suddenly got exception messages like :"Connection must be valid and open / connection already open". It seemed that datacontext was not disposed. The only change, according to me, was the data size and number of users increasing.
I then found multiple posts saying that singleton was a bad idea foe datacontext, so I tried to instanciate datacontext in a using statement in every request and that resolved the problem, except for update queries which had no effects in database. I had to attach the db object to the context and then set its EntityState to "modified" to have my SaveChanges work.
Like this :
public bool DoucheXpsu(as_headers session) {
using (MyDBEntities MyContext = new MyDBEntities()) {
try {
as_status status = GetStatus(session);
if (status != null) {
if (status.mainstatusvalue == 300) {
status.DateDoucheXpsu = DateTime.Now;
status.DoucheXpsu = 1;
MyContext.as_status.Attach(status);
MyContext.ObjectStateManager.ChangeObjectState(status, EntityState.Modified);
MyContext.SaveChanges();
return true;
} else {
return false;
}
} else {
return false;
}
} catch (OptimisticConcurrencyException) {
return false;
} catch (Exception) {
return false;
}
}
}
The problem is that it actually didn't work for ONE method (which has nothing different from the other update method) !
The exception occured as I tried to attach the object : "The object cannot be attached because it is already in the object context. An object can only be reattached when it is in an unchanged state. " So I had to comment the attach and ChangeObjectState methods to have it work as expected :
public bool SetSessionToDelete(string numSession) {
using (MyDBEntities MyContext = new MyDBEntities()) {
try {
view_headerStatus view = (from v in MyContext.view_headerStatus
where v.CodeSession == numSession
where v.lastinserted == 1
select v).First();
if (view != null) {
as_status status = (from s in MyContext.as_status
where s.jobclsid == view.jobclsid
where s.lastinserted == 1
select s).First();
if (status != null) {
status.DeleteSession = 1;
//MyContext.as_status.Attach(status);
//MyContext.ObjectStateManager.ChangeObjectState(status, EntityState.Modified);
MyContext.SaveChanges();
return true;
} else {
return false;
}
} else {
return false;
}
} catch (OptimisticConcurrencyException) {
return false;
} catch (Exception) {
return false;
}
}
}
The question is WHY should this one behave differently ???
I've read many posts about EF and dataContext but I feel I'm missing something. I would be glad if anyone can help.
Thanks.
In your first example, this line here:
as_status status = GetStatus(session);
I would assume this populates using a DIFFERENT context, and when it leaves the GetStatus() method the context it used to load is disposed. That is why your subsequent Attach() works. However in your second example you do not need to attach because it was loaded using the current (connected) context.
To solve you may want to either pass the context to your methods like GetStatus() resulting in no need to reattach. I don't typically reattach unless I am resurrecting an object over the wire or from a file.