Using the Java Reflection (reflection) principle, the dynamic combination query of Tanku and view in Hibernate is implemented.

Dynamic | view | combination Query
Reflection is one of the characteristics of Java program development language, it allows the running program to access itself, and can directly manipulate the internal properties of the program.



Hibernate is a Java environment-oriented object/relational database mapping tool, basically, each table or view in the hibernate can correspond to a class, where we make full use of this class, to implement dynamic combinatorial query.



First, let's take a look at the source code for this function:



   /**     * Combined Query      * @param object contains query criteria       * @param firstresult the first return position (starting from 0)      * @param maxresults Maximum number of returns    & nbsp * @param orderfield  sorted fields      * @param isabs are in a positive order      * @return  & nbsp;   * @throws hibernateexception     */    public List queryList ( Object object, int firstresult, int maxresults,string OrderField, Boolean isasc) throws Hibernateexception, Illegalargumentexception,illegalaccessexception,invocationtargetexception {         List list=null;        Class c = object.getclass ();         method method[] = C.getmethods ();        try {             Session session = CurrentsessIon ();            criteria = Session.createcriteria (Object.getclass ());            for (int i = 0; i < method.length i++) {            & nbsp;   String name = Method[i].getname ();                 if (Name.indexof ("Getmin") ==0) {   //greater than                      String fieldName = Name.substring (6, 7). toLowerCase () + name.substring (7);                     Object retobj = Method[i].invoke (object, NULL);                     if (Retobj!= NULL&&!retobj.equals (""))                          Criteria.add (expression.ge (FieldName, retobj));                      continue;               }                 if (Name.indexof (" Getmax ") ==0) {//less than                      String fieldName = name.substring (6, 7). toLowerCase () + name.substring (7);                     Object retobj = Method[i].invoke (object, NULL);                     if (retobj!= null &&!retobj.equals (""))        & nbsp;                Criteria.add ( Expression.le (FieldName, retobj));                     continue;                }                 if (Name.indexof ("get")!= 0 | | | name.indexof ("getclass") = = 0)  //If not required method, jump out                      continue ;                String fieldName = Name.substring (3, 4). toLowerCase () + name.substring (4);                 String returntype = Method[i].getreturntype (). toString ();                 Object retobj = Method[i].invoke (object, NULL);                 if (retobj!= null) {     //If NULL, no value assigned, jump out                      if (Returntype.indexof ("String")!=-1) {                          if (Retobj.equals ("))     //If the string field is" ", jump out of                              continue;                         Criteria.add (Expression.like (fieldName, "%" + retobj + "%"));   For string fields, use the like Blur query                     }else                         Criteria.add (Expression.like (FieldName, retobj));                   }           }             if (ISASC)                  Criteria.addorder (ORDER.ASC (OrderField));   //Ascending              else                 Criteria.addorder (Order.desc (OrderField));   //Descending              Criteria.setfirstresult (Firstresult);             criteria.setmaxresults (maxresults);             list = Criteria.list ();       } finally {             closesession ();        }



return list; }



Suppose the relational database has a physical table with the following structure:



STAFF (Employee table)



Column Name



Type



Null



Description



Id (PK)



VARCHAR2 (20)



Not NULL



Employee work number



Name



VARCHAR2 (20)



Not NULL



Employee Name



Dept



INTEGER



Null



Department of employee (P3)



Password



VARCHAR2 (20)



Not NULL



Password



Post



INTEGER



Null



Position of employee (P14)



Priv



VARCHAR2 (40)



Not NULL



Permission Word



Birthday



VARCHAR2 (20)



Null



Birthday



Active



VARCHAR2 (1)



Not NULL



Y: Activating N: Inactive



Use the tool to generate its associated Hibernate class staff, which includes the following fields:



Private java.lang.String ID;    private java.lang.String name;    Private Java.lang.Long Dept;    private java.lang.String password;    Private Java.lang.Long Post;    Private Java.lang.String Priv;    Private java.lang.String birthday; Private java.lang.String active;







Below, we can use the above querylist to carry on the query



Example 1:



The front desk needs a list of all the people,



So the relevant code is as follows:



Staff staff=new Staff ();



List list=querylist (staff,0,1000,id,true);







Example 2:



Find people with "ding" in all their names



So the relevant code is as follows:



Staff staff=new Staff ();



Staff.setname= "Ding";



List list=querylist (staff,0,1000,id,true);







Example 3:



Query for all names that contain "ding" and who are in the active state



So the relevant code is as follows:



Staff staff=new Staff ();



Staff.setname= "Ding";



Staff.setactive= "Y";



List list=querylist (staff,0,1000,id,true);





Example 4:

Query all people whose names contain "ding" and are active, and ask the returned list to be sorted by birthday



So the relevant code is as follows:



Staff staff=new Staff ();



Staff.setname= "Ding";



Staff.setactive= "Y";



List list=querylist (Staff,0,1000,birthday,true,);







To staff processing, you can achieve greater than, less than the function, such as we want to implement query after 1981-09-16 people, then you can add the following code in the Staff class:

Private java.lang.String Minbirthday;



Private java.lang.String Maxbirthday;



Public java.lang.String Getminbirthday () {

return minbirthday;

}

public void Setminbirthday (java.lang.String minbirthday) {

This.minbirthday = Minbirthday;

}

Public java.lang.String Getmaxbirthday () {

return maxbirthday;

}

public void Setmaxbirthday (java.lang.String maxbirthday) {

This.maxbirthday = Maxbirthday;

}





Example 5:

Query birthday After 1978 years, before 1981, the activation status of personnel, required name contains "Ding", in descending order of birthdays

Staff staff=new Staff ();



Staff.setname= "Ding";



Staff.setactive= "Y";



Staff. Setminbirthday ("1978");



Staff. Setmaxbirthday ("1981");



List list=querylist (Staff,0,1000,birthday,false);

So far, it should be said that the introduction of almost, perhaps someone to ask, "a single table query, you can do so, then the table query how to do?" "In fact, it is very simple to create a view within the database." I hope this experience will be useful to you.