hibernate - JPA criteria query, order on class -

-

is there way jpa criteria queries order on class? imagine following domain objects:

abstract class hobby { ... } class coding extends hobby { ... } class gaming extends hobby { ... }

using regular ql able do

from hobby h order h.class

but when apply same logic on criteria query, runtime exception "unknown attribute" occurs.

criteriaquery<hobby> criteriaquery = builder.createquery(hobby.class); root<hobby> hobbyroot = criteriaquery.from(hobby.class); criteriaquery.orderby(builder.asc(hobbyroot.get("class")); list<hobby> hobbies = entitymanager.createquery(criteriaquery).getresultlist();

jpa implementation used: hibernate-entitymanager v3.5.5-final

jpa 2.0 introduces new type expression allow query restrict results based on class types.

you can use type expression criteria api using path#type(). try:

criteriaquery criteriaquery = builder.createquery(hobby.class); root hobbyroot = criteriaquery.from(hobby.class); criteriaquery.orderby(builder.asc(hobbyroot.type()); list hobbies = entitymanager.createquery(criteriaquery).getresultlist();

while code compiles, didn't test (i'll give try tomorrow).

actually, wonder if legal or if type() should part of select in order order by (maybe that's criteria query supposed generate). need check that.

references

  • jpa 2.0 specification
    • section 4.6.17.4 "entity type expressions"

more resources


Comments

Post a Comment

Popular posts from this blog

android - Spacing between the stars of a rating bar? -

-
ho can set spacing beween stars? thats ratingbar: ratingbar = (ratingbar) inflater.inflate(r.layout.ratingbar, null); ratingbar.setlayoutparams(new layoutparams(layoutparams.wrap_content, layoutparams.wrap_content)); the layout: <?xml version="1.0" encoding="utf-8"?> <ratingbar xmlns:android="http://schemas.android.com/apk/res/android" style="@style/mystyle" android:layout_alignparentright="true" android:layout_height="19dp" android:layout_width="wrap_content" android:numstars="5"> </ratingbar> the style: <style name="mystyle" parent="@android:style/widget.ratingbar"> <item name="android:progressdrawable">@drawable/android_r2_ratingstar_yellow</item> <item name="android:indeterminatedrawable">@drawable/android_r2_ratingstar_grey</item> </style> thanks, cheers you have ...
Read more

html - Instapaper-like algorithm -

-
does of algorithm extracts contents webpage? instapaper ? there 2 steps instapaper does: find main content block on page (excluding headers, footers, menus etc) from content block extract , format text to find content block (typically html block element, div containing key page text content) instapaper uses algorithm 1 used readability . can @ source of readability.js see what's going on, @ core tries find area on page highest text/link ratio, although has other simple scoring metrics (e.g. off top of head, things ratio of text commas, para elements etc) go heuristics. once have identified root node element, relevant content, you'll need format it, if want can pull node element containing text out of source document , insert yours, in reality you'll want remove existing styles , apply own, standard , feel. if want output nice text-only can use jericho's renderer . update1 : should mention else instapaper - follow 'pagination' links (...
Read more

c# - How to execute a particular part of code asynchronously in a class -

-
i creating speech recognition engine that's going respond user commands.i have created button enable , disable speech recognition per user convenience.i have used dispose() of speech engine disable speech recoginition.here code private void button1_click(object sender, routedeventargs e) { engineon = !engineon; if (engineon) { speechengine = speech.createspeechengine(); //speech class creates , returns new speech engine. speechengine.audiolevelupdated += new eventhandler<audiolevelupdatedeventargs>(speechengine_audiolevelupdated); // use system's default microphone speechengine.setinputtodefaultaudiodevice(); speechengine.loadgrammar(new dictationgrammar()); // start listening speechengine.recognizeasync(recognizemode.multiple); } else { speechclass.myengine.dispose(); } } but disposal of speech obj...
Read more