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1 package com.db4o.f1.chapter5;
2
3 import java.io.*;
4 import com.db4o.*;
5 import com.db4o.f1.*;
6
7
8 public class DeepExample extends Util {
9 public static void main(String  [] args) {
10 new File(Util.YAPFILENAME).delete();
11 ObjectContainer db=Db4o.openFile(Util.YAPFILENAME);
12 try {
13 storeCar(db);
14 db.close();
15 setCascadeOnUpdate();
16 db=Db4o.openFile(Util.YAPFILENAME);
17 takeManySnapshots(db);
18 db.close();
19 db=Db4o.openFile(Util.YAPFILENAME);
20 retrieveAllSnapshots(db);
21 db.close();
22 db=Db4o.openFile(Util.YAPFILENAME);
23 retrieveSnapshotsSequentially(db);
24 retrieveSnapshotsSequentiallyImproved(db);
25 db.close();
26 setActivationDepth();
27 db=Db4o.openFile(Util.YAPFILENAME);
28 retrieveSnapshotsSequentially(db);
29 }
30 finally {
31 db.close();
32 }
33 }
34
35 public static void storeCar(ObjectContainer db) {
36 Pilot pilot=new Pilot("Rubens Barrichello",99);
37 Car car=new Car("BMW");
38 car.setPilot(pilot);
39 db.set(car);
40 }
41
42 public static void setCascadeOnUpdate() {
43 Db4o.configure().objectClass(Car.class).cascadeOnUpdate(true);
44 }
45
46 public static void takeManySnapshots(ObjectContainer db) {
47 ObjectSet result=db.get(Car.class);
48 Car car=(Car)result.next();
49 for(int i=0;i<5;i++) {
50 car.snapshot();
51 }
52 db.set(car);
53 }
54
55 public static void retrieveAllSnapshots(ObjectContainer db) {
56 ObjectSet result=db.get(SensorReadout.class);
57 while(result.hasNext()) {
58 System.out.println(result.next());
59 }
60 }
61
62 public static void retrieveSnapshotsSequentially(
63 ObjectContainer db) {
64 ObjectSet result=db.get(Car.class);
65 Car car=(Car)result.next();
66 SensorReadout readout=car.getHistory();
67 while(readout!=null) {
68 System.out.println(readout);
69 readout=readout.getNext();
70 }
71 }
72
73 public static void retrieveSnapshotsSequentiallyImproved(
74 ObjectContainer db) {
75 ObjectSet result=db.get(Car.class);
76 Car car=(Car)result.next();
77 SensorReadout readout=car.getHistory();
78 while(readout!=null) {
79 db.activate(readout,1);
80 System.out.println(readout);
81 readout=readout.getNext();
82 }
83 }
84
85 public static void setActivationDepth() {
86 Db4o.configure().objectClass(TemperatureSensorReadout.class)
87 .cascadeOnActivate(true);
88 }
89 }
90 |
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Java API By Example, From Geeks To Geeks.