HELP! Newbie: Unable to update fields

Question

Hello.
I am teacher of a Java course and I am teaching Kodo JDO to my students. But
I am unable to update my persistent fields to the DB. I have a persistent
class Employee with two fields: name and wage. I have the following code:
PersistenceManager pm = JDOFactory.getPersistenceManager();
Transaction tran = pm.currentTransaction();
fillDatabase(pm,tran);
Employee john = getJohn(pm);
tran.begin();
System.out.println("Before update" + determineState(john));
john.wage = 20000.;
System.out.println("After update" + determineState(john));
tran.commit();
pm.close();
Employee John never gets updated to the DB. The program has the following
output:
Before update. Persistent-Clean-NonTransactional
After update. Persistent-Clean-NonTransactional
That is, the field doesn't get dirty.
I attach all the source code to this message. It's a very simple example.
What am I doing wrong? How can I persist my updates to the DB?
Please I'm desperate. I don't know how to do and I need this solution for
tomorrow afternoon (I have class with my students then).
Any help would be gretly appreciated.
Thank you,
Vicent Palas__
begin 666 kodoHELP.zip
M4$L#!!0````(`$H).RVD)9P]$ (``$8$```/````:V]D;RYP<F]P97)T:65S
M?5-=;]I $'R/Q']8*2^M!":!2DA(?BFHJA*24)KV?3FO[2-WM_3N#+B_OGM
MFU0!7C#RS,[LQ_@:[KE@N)L^P=SSFGS4%$"Q*W75>(R:7>>J<W4-SPRT0=-@
M)& /Z\:K&@,!@M&*G/Q[H;8+&QUTA#K&];C?WVZW66"#WE+T6F6*;>=*?OY[
M^2+^V>R@<4]M/AP,:#@<]G!X6]X.1KT1EOAI.>A1.2IOAJ-S`EQ5Y/,0"V[B
M&0Y1]H .*RH6C8O:TNO$^;-'%U"E>0\<_XB6\A5N<-Q_#Z:=)&R7K41X3C[H
M$,DI.N)?A,V^G1@,(3_9C+9K(\5+E=U-/T_.*KRUX77J()NP<[1O9NKUYM@H
M^RJK5C&S-K-M^&6R`W:Q_$<X%GOF>)$YES&V[(N\EC$N:RYF>9IJO.]",F!8
MH:DYQ#ZM2&9FB=H)A2=Y6-F 5GGT#9U@+"BB=C\E@G*N,YQ'=O'U5F@6A,61
MFS(\J=%5VE40:Y+ 1I;T.G:]W^094K@)MMH8*#Q:B;XT;EK03GF2I"<!24O)
MWJ*<J0O+)A[H"AM1TZYGR<K)H,"(2ZD($!I5`P;XVDIE8*=54OG^;9:\'<F!
M@';RO6QK<M!RX\'*C!\^@B2EYF(/AFY2D(YAS6RH2 KJW[Z#^.[!]_9OFT-Y
M*VBBRC"%V"<93\D.?..<;"4[L= '[>;BFM^<PG#W%_L#4$L#!!0````(``('
M.RV(V,<BAP(``)P&```1````5&5S=$5M<&QO>65E+FIA=F&55$UOVS ,/;M
[email protected][TFPM9CBV#8V@U#@;4=TMNZ@^(PF3)9,B2Y23#TOX^29<=MTP[5Q30_
M'LE'4;*JC?6 5:W,#M'Q=V>C(]DJU^)>;/EZ89XJ>>.EBLK14=W,E2RA5,(Y
MN$7GOR0H^#LZ`LB2W7GAZ7-OY (J(37D,V^E7H&P*_?S5T'.&="Y0>ND\ZA+
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MG^]!_@]Z$^ACXY.WH4;.0NT]L2V'SQ:BS]3=J%>(*^)&`7&U#0D!P\<%$J>]
M3]B.UIQWT#SNYIB8;J@R2!@_&K0[*(UVC?)BB$ $1&/>XX^9%A5Q,[V+'-\Q
M8&EWLNS<*(7M*,L@$E*^UQ5=`HY;+!N/:8P6?6/I$>@9B[%<$M>"ECPOJ(JM
M3QL:B'MVY=+S\>1V7\_7E!CJLH!XJY*7HZH8BYD='%.%])Q\0U53M](-1ACB
M/@+;:]@IBY=5!KEX`>!"6K_K8B?QC\$IFYPK%/K%J"O<]#$DAXB7,Z"B/A?[
M'.W_($8N7VLJL7$`>;"*0G7XU/7DRF@_M*4\X1W(4#E\"V+T9)-'%M:7_C"X
M$"[M29SX/U!+`P04````" "5`CLM8T'@/5,```!M````#0```&5M<&QO>65E
M<RYJ9&^SL:_(S5$H2RTJSLS/LU4RU#-0LK?CY;+)2LD'4IPV!8G)V8GIJ0IY
MB;FIMDJIN04Y^96IJ<5*($D%!9ODG,3B8JBD*U1221^L4Q^J%62:/L0X`%!+
M`P0*``````#1"3LMVC!\3H$#``"!`P``#0```&5M<&QO>65E<RYZ:7!02P,$
M% ````@`.0<[+8G*6Z^ ````S@````T```!%;7!L;WEE92YJ879A*TA,SDY,
M3U5(S2W(R:],32VVYN7BY2HH3<K)3%9(SDDL+E9PA4HI5/-R<4)E@DN*,O/2
M%?(2<U.M$:(I^4 Z5:$<:"#8& 4%F S,# V8QM1R/Z!>'9@6(#\<J$NSFA.H
MAQ.L4P$(0.8KV,)4@VSB!!D.$0J'6,-9"\2\7+4@"P%02P,$% ````@`L 8[
M+<!N;LL;`@``%P4```\```!*1$]&86-T;W)Y+FIA=F&-4]MNVS ,?5: _ .1
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M_9YE4$@$BZA-`H!*VQ)]XJ^2I)903:\^;Q1ZTFFPVN'H6!0M@WOD!GCO),W4
M$@8KS:&F"*T&EZXUC1T2,%LH&F'X3-JP'KQCHKT6_F<CI5UWQGQAP7SXX)JD
MZQL:WTWGA?7Q'#I*[CYTOBI .?YTRGL2SO-E^O O^OF$$^!F)+7%!N;!K5(#
MZ78RA. [,XQOL^[;'?M_JQYYM'3WBJ/K4S!E'.G]`U!+`0(6"Q0````(`#D'
M.RV)RENO@ ```,X````-``````````$`( " @0````!%;7!L;WEE92YJ879A
M4$L!`A8+% ````@`L 8[+<!N;LL;`@``%P4```\``````````0`@`("!JP``
M`$I$3T9A8W1O<GDN:F%V85!+!08``````@`"`'@```#S`@````!02P$"%@L4
M````" !*"3LMI"6</1 "``!&! ``#P`````````!`" `@($`````:V]D;RYP
M<F]P97)T:65S4$L!`A8+% ````@``@<[+8C8QR*'`@``G 8``!$`````````
M`0`@`("!/0(``%1E<W1%;7!L;WEE92YJ879A4$L!`A8+% ````@`E0([+6-!
MX#U3````;0````T``````````0`@`("!\P0``&5M<&QO>65E<RYJ9&]02P$"
M%@L*``````#1"3LMVC!\3H$#``"!`P``#0```````````" `@(%Q!0``96UP
@;&]Y965S+GII<%!+!08`````! `$`/(````="0``````
`
end

Answer 1

Thank you very much, Abe.
Of course, I always advocate the benefits of encapsulation with my students.
In this example, I declared my fields as public only because I was trying
with private fields and it wasn't working (I don't know why). So I try with
public fields to see whether it would work.
Anyway, I had encapsulated my fields and everything worked OK. I was in
trouble (the class is only some hours away and some of my students are
prospects of customers so my image is fundamental). You have get me out of
trouble.
Thank you for your help.
Vicent Palas__
"Abe White" <[email protected]> escribi__ en el mensaje
news:an1rrf$bnk$[email protected]..
john.wage = 20000.;JDO detects field updates by modifying the bytecode of the class accessing
the field. When you use public fields, that means all classes thataccess
the fields need to be run through the enhancer, even if some of thoseclasses
are not persistent themselves (note: only persistent classes
should have metadata -- the enhancer uses the presence of metadata to
determine whether to make the class persistent or just modify persistent
field access to other classes).
Because it's a pain to track which non-persistent classes accesspersistent
fields of persistent classes, we recommend that you keep your persistent
fields private, or protected and only accessed by subclasses. Plus, as a
teacher, I would think you'd be advocating the benefits of encapsulation
anyway :)