I have a siftingappender that i use for a key in mdc to customize the file appenders. The problem is i cannot access multiple values from the configuration.
Is there a way to access 2 or more keys that exists in MDC?
I had the same problem, and looking at the class it appeared it wasn't possible to use two discriminator keys. The solution I used was then to set a property containing the combination of this values at the beginning of the "session" :
String value1 = "a variable";
String username = "the username";
MDC.put("myDiscriminatingValue", value1 + username);
and then you just have to put "myDiscriminatingValue" in logback.xml as a discriminating value.
A more elegant way to achieve it would be to implement your own Discriminator class instead of MDCBasedDicriminator.
Related
I want to organize some part of my system, but i can't choose convenient form for data representation for interaction with my app.
So i have some local "repository" of data object, descripted as follows:
Object1
{ id = TypeId, field1 = value1, otherObjectSpecifedField = value2 ... }
...
There are many objects (for example 1000) of many types (for example 50). Each type have it own UniqueId and his own description and set of fields.
Next thing is that for each object i have a set of filters, which corresponds that this object is actual right now. It looks like this:
Filter
{ filterName1 = filterValue, filterName2 < filterValue }
Object // filter is applied for this object
{ ... }
The process of using this "repository":
In my app i have application states, which means filters from above.
Example: application localization can be 'en' (my application knows this value and can change it on start) and we have filter, named 'localization' and in our repository we can use it like this:
Filter { localization = 'en'}
Object1 { ... } // this object i should choose when localization is en
When my app decides to check which set of obects is actual right now it cames to repository and asks it: "Here you an TypeId and please, walk through each filter+object pair and say what object is actual by filters. If you need to resolve some filter values (localization from example above) i will resolve them for you".
Then repository walks through each object and compare which is actual by filters now, and which is not and give actual to app. So he check every filter of every object and gives it only if all of them is actual and he did it in runtime.
In current implementation this set of fiters + objects is stored in xml file in very specific xml format, which is comfortably to read from app, but very hard to maintain by human. And i think that there is some place to optimization of all process. I think we can delegate of walking through Objects and comparing it filters to someone else.
Now i think in side of NoSQL document oriented databases. Because each Object has his unique structure and maybe using select routine i can choose what i need.
Maybe someone have any suggestions about that type of database organization? Maybe you know some specific data structure for that type of data?
Maybe I've missed something, because it looks to me like you have a number of different types of objects: one type per TypeId. If that's so, then I think this can be done with a standard SQL database, assuming that the fields within an object have a consistent type. If not, it can still be done with a NoSQL database.
In a SQL database, you would use a separate table for each type (since they each have their own set of fields), and search across the appropriate table with SQL. So, for example, you can create a table with two fields (I'm using SQLite here, which doesn't require types for fields):
create table Object1 (field1, otherObjectSpecifiedField);
This table can then have data inserted into it:
insert into Object1 values ("field1value", "otherfieldValue");
Filtering uses standard SQL:
select * from Object1 where field1 = "field1value";
As I mentioned, this could also be done with a NoSQL database such as MongoDB. That would look something like this in the Mongo CLI:
Create table and insert first object:
db.test.insert({ id: "TypeId", field1: "value1", otherObjectSpecifedField: "value2"});
Select an object from the table:
db.test.find({id: "TypeId", field1: "value1"});
/* { "_id" : ObjectId("57cf97060216d33b891615ba"), "id" : "TypeId", "field1" : "value1", "otherObjectSpecifedField" : "value2" } */
I am trying to use a loop to access some variable information within a class module in Access 2016.
If I am using a DAO instance such as rst!Name, and want to use a variable in a loop I can substitute to this version, rst(variable), where variable = "FirstName" or some other field name to get the same answer.
If I am accessing the field "FirstName" from within a class named "clsPerson" with a line such as clsPerson.FirstName, and want to use a variable for the field name ("FirstName" or others such as "Address", etc. provided by a loop), is there a way to code that in VBA? In DAO I would use clsPerson("FirstName") but that doesn't seem to work. Is there something that does?
You could create a "common" property like:
clsPerson.CommonProperty("FirstName")
and in this have a Select Case construct to get/set the actual clsPerson.FirstName.
But that's about it.
I have been struggling with an issue for a couple of days. I am sharing a Content Provider with two different apps (app A and app B). All the stuff regarding DB creation and Content Provider management is done by app A. App B just accesses it using the corresponding Authorities and a Content Provider Client.
ContentProviderClient myCPClient = this.miContext.getContentResolver().acquireContentProviderClient(this.miUri);
The problem comes up when trying to query the database in a more complex way, i.e. using some key words like GROUP BY, HAVING, etc. I need to get unique references according to one specific column (I want to use GROUP BY), and I have found out that there is no rawQuery() method for a ContentProviderClient, but a simplified query() method (compared to the one available in the class SQLiteDatabase, which allows to formulate proper MySQL commands).
I have checked this answer, but since my ContentProvider is accessed from a different app, I do not have any class like MyContentProvider.
To sum up, is there any way to make a proper query (like rawQuery()) to a ContentProvider which was generated by a different app?
I have finally got to a solution which is rather simple and sensible. I got a very good explanation about Content Providers and Content Resolvers. The latter is used to access the former, which means that they can not control what is in the provider, but get data from them. This means that you can not make a Content Provider Client to use a rawQuery() if it is not implemented (override) in the query() method of the corresponding ContentProvider.
To work around my problem, I have used a flag in my provider client and modify my content provider to read it so I can make use of GROUP BY. I just wanted to get unique references from the database according to a particular column.
Here it is the solution, which is not a very clean one, but it works quite well.
For the ContentProviderClient,
ContentProviderClient myCPClient = this.miContext.getContentResolver().acquireContentProviderClient(this.miUri);
//I declare some variables for the query
//'selection' will get all the rows whose "_id" is greater than 0, i.e. all the rows
String selection = BaseDatosParam.Tabla._ID + ">?";
String[] selectionArgs = {"0"};
//'groupBy' is not formatted in any particular way. I just need it to contain the pattern "GROUP BY"
String groupBy = "GROUP BY" + BaseDatosParam.Tabla.REF;
//the last field of the query corresponds to 'sortOrder', but I
Cursor c = myCPClient.query(Uri.parse(miUri.toString()),
projection, selection, selectionArgs, groupBy);
In the ContentProvider,
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
{
String where = selection;
String groupBy = null;
SQLiteDatabase db = this.miBDManager.getWritableDatabase();
//We just check out whether 'sortOrder' includes the pattern "GROUP BY", otherwise that field will remain null
Pattern myPat = Pattern.compile("GROUP BY");
Matcher myMat = myPat.matcher(sortOrder);
if (myMat.find())
groupBy = myMat.replaceFirst("");
Cursor c = db.query(BaseDatosParam.Tabla.NOMBRE_TABLA, projection, where, selectionArgs, groupBy, null, null);
c.setNotificationUri(this.getContext().getContentResolver(), uri);
return c;
}
Regards,
Is it possible to create an index on a Boolean type field?
Lets say the schema of the records I want to store is:
{
id:1,
name:"Kris",
_dirty:true
}
I created normal not unique index (onupgradeneeded):
...
store.createIndex("dirty","_dirty",{ unique: false })
...
The index is created, but it is empty! - In the index IndexedDB browser there are no records with Boolean values - only Strings, Numbers and Dates or even Arrays.
I am using Chrome 25 canary
I would like to find all records that have _dirty attribute set to true - do I have to modify _dirty to string or int then?
Yes, boolean is not a valid key.
If you must, of course you can resolve to 1 and 0.
But it is for good reason. Indexing boolean value is not informative. In your above case, you can do table scan and filter on-the-fly, rather than index query.
The answer marked as checked is not entirely correct.
You cannot create an index on a property that contains values of the Boolean JavaScript type. That part of the other answer is correct. If you have an object like var obj = {isActive: true};, trying to create an index on obj.isActive will not work and the browser will report an error message.
However, you can easily simulate the desired result. indexedDB does not insert properties that are not present in an object into an index. Therefore, you can define a property to represent true, and not define the property to represent false. When the property exists, the object will appear in the index. When the property does not exist, the object will not appear in the index.
Example
For example, suppose you have an object store of 'obj' objects. Suppose you want to create a boolean-like index on the isActive property of these objects.
Start by creating an index on the isActive property. In the onupgradeneeded callback function, use store.createIndex('isActive','isActive');
To represent 'true' for an object, simply use obj.isActive = 1;. Then add or put the object into the object store. When you want to query for all objects where isActive is set, you simply use db.transaction('store').index('isActive').openCursor();.
To represent false, simply use delete obj.isActive; and then add or or put the object into the object store.
When you query for all objects where isActive is set, these objects that are missing the isActive property (because it was deleted or never set) will not appear when iterating with the cursor.
Voila, a boolean index.
Performance notes
Opening a cursor on an index like was done in the example used here will provide good performance. The difference in performance is not noticeable with small data, but it is extremely noticeable when storing a larger amount of objects. There is no need to adopt some third party library to accomplish 'boolean indices'. This is a mundane and simple feature you can do on your own. You should try to use the native functionality as much as possible.
Boolean properties describe the exclusive state (Active/Inactive), 'On/Off', 'Enabled/Disabled', 'Yes/No'. You can use these value pairs instead of Boolean in JS data model for readability. Also this tactic allow to add other states ('NotSet', for situation if something was not configured in object, etc.)...
I've used 0 and 1 instead of boolean type.
Can I use partial classes to create properties that points to an association property generated by the L2S designer. Also, will I be able to use the new property in queries?
How can I achieve this?
If you just want to give a different name to the association property, just use the Property page for the association and rename the parent and/or child property. That will change the name of the EntityRef/EntitySet in the class.
EDIT: The downside of using a separate property in a partial class is that LINQ won't be able to use it when generating queries -- essentially you'll be forced to always get the entities before you can use the related properties on the object. By renaming you allow LINQ to use the related properties in constructing the query which can result in a more efficient query. For example, if you want to get entities where a related entity has a particular property value, using the attribute decorated entity will allow LINQ to generate the SQL to pull just those matching values from the database. With the naive property implementation (that simply references the underlying relation property, in effect renaming it), you will be forced to first get all entities, then do the filtering in your application.
Yes you can, but you have to apply the same attributes as the linq2sql generated property i.e.
[Association(Name="Test_TestData", Storage="_TestDatas", ThisKey="SomeId", OtherKey="OtherId")]
public System.Data.Linq.EntitySet<TestData> MyTestDatas
{
get
{
return this.TestDatas;
}
}
TestDatas being the original relation.
Update: A sample query I ran:
var context = new DataClasses1DataContext();
var tests =
from d in context.Tests
where d.MyTestDatas.Any(md=>md.MyId == 2)
select new
{
SomeId = d.SomeId,
SomeData = d.SomeData,
Tests = d.MyTestDatas
};
foreach (var test in tests)
{
var data = test.Tests.ToList();
}