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How to call methods with indexes

 
René van der ven
Greenhorn
Posts: 8
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I have lots of methods, which are almost the same, apart from the object name and the name of setters and getters.
What I would like to achieve is:

fill_DocLine(ResultSet rs, DocLine, [Index method, Input value ...
fill_DocLine(ResultSet rs, DocLine, [3, rs.getInt(1)], [4, rs.getString(2)], 6, rs.getInt(3)] ) {

DocLine refers to the Java Object to fill, and 3,4,6 refers to the indexes of the methods

DocLine line = new DocLine();
line.setNo(rs.getInt(1)); //method index 3 = setNo
line.setText(rs.getString(2)); //method index 4 = setText
line.setType(rs.getInt(3)); //method index 6 = setType

I heard of reflection, can I achieve this with reflection, if so how.
 
Claude Moore
Ranch Hand
Posts: 829
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IBM DB2 Java Netbeans IDE
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Hi Renè,

IMHO the main flaw with your approach is that you need indexing your set methods, because Java reflection doesn't keep any order by itself on declared methods
or fields of a class. Moreover, you need to keep in sync ordering of the columns in the query with ordering of the setter methods: what about if instead of
"SELECT ALFA, BETA FROM TABLE " you run a "SELECT GAMMA, ALFA, BETA FROM TABLE " ?

You may try and write a custom annotation which let you to map a field of your DocLine class with a column of the select, for example



After getting a ResultSet from your query, you may want to use ResultSetMetaData and get retrieved columns' names, and follow a similar pseudo-code



Of course an heavy usage of reflection causes the code to run slower, but it may be a first step towards reading cursors
automatically instead of writing boilerplate code.

By the way: this it's just the role played by Persistence Engines like JPA or Hibernate: they do something similar of what
I described you, but, of course, in a smarted and cleverer way... but if you want to play with JDBC that may be an interesting starting point.



 
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