So I was looking around Hibernate's API and found the QBE bit which seems to be
handy for simple queries. I then wondered how I could go about something
similar in Seam. I didn't want to open up my own Hibernate Session and
consequently manage that Session, so I came up with a little utility method for
QBE. Granted this example is very limited and simplistic, but I could see it
coming in handy for some of the simpler queries.
| public class QueryUtils {
| ...
| public static <T> List<T> queryByExample(T example, EntityManager em){
| Class clazz = example.getClass();
| StringBuffer q = new StringBuffer("from " + clazz.getName() + "
obj");
| Map<String, Object> params = new HashMap<String, Object>();
| Field[] fields = clazz.getDeclaredFields();
| boolean isFirstClause = true;
| for(Field field: fields){
| String getterName = "get" +
StringUtils.capitalize(field.getName());
| try{
| Method getter =
clazz.getDeclaredMethod(getterName, new Class[0]);
| Object propertyValue = getter.invoke(example,
new Object[0]);
| if(propertyValue != null){
| if(isFirstClause){
| q.append(" where ");
| }else{
| q.append(" and ");
| }
| q.append("obj." + field.getName() + " =
:" + field.getName());
| params.put(field.getName(),
propertyValue);
| isFirstClause = false;
| }
| }catch(NoSuchMethodException nsme){
| //do nothing for now
| }catch(InvocationTargetException ite){
| //do nothing for now
| }catch(IllegalAccessException iae){
| //do nothing for now
| }
| }
| Query query = em.createQuery(q.toString());
| for(String key: params.keySet()){
| query.setParameter(key, params.get(key));
| }
| System.out.println(q.toString());
| return query.getResultList();
| }
| ...
|
Also, I wanted to mention that QBE inherently does not include any way to
search, say, within a date range or an integer range if your bean so happens to
have a date or integer property. In this case, would you just opt not to use
QBE at all, or do you go into adding Expressions via hints? The end goal is to
be able to make otherwise long/tedious queries simply by providing an example
(and perhaps also expressions for ranged properties). I just wanted to present
this to the community and see what others are doing.
View the original post :
http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4007946#4007946
Reply to the post :
http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4007946
_______________________________________________
jboss-user mailing list
jboss-user@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/jboss-user
