|
1 package com.db4odoc.f1.queries;
2
3 import java.io.File  ;
4
5 import com.db4o.Db4o;
6 import com.db4o.ObjectContainer;
7 import com.db4o.ObjectSet;
8 import com.db4o.query.Constraint;
9 import com.db4o.query.Query;
10
11
12 public class QueryExample {
13 public final static String YAPFILENAME="formula1.yap";
14
15 public static void main(String [] args) {
16 storePilot();
17 updatePilotWrong();
18 updatePilot();
19 deletePilot();
20 ObjectContainer db=Db4o.openFile(YAPFILENAME);
21 try {
22 retrievePilotByName(db);
23 retrievePilotByExactPoints(db);
24 retrieveByNegation(db);
25 retrieveByConjunction(db);
26 retrieveByDisjunction(db);
27 retrieveByComparison(db);
28 retrieveByDefaultFieldValue(db);
29 retrieveSorted(db);
30 } finally {
31 db.close();
32 }
33 }
34
36 public static void storePilot() {
37 new File (YAPFILENAME).delete();
38 ObjectContainer db=Db4o.openFile(YAPFILENAME);
39 try {
40 Pilot pilot=new Pilot("Michael Schumacher",0);
41 db.set(pilot);
42 System.out.println("Stored "+pilot);
43 pilot.addPoints(10);
45 db.set(pilot);
46 System.out.println("Stored "+pilot);
47 } finally {
48 db.close();
49 }
50 retrieveAllPilots();
51 }
52
54
55 public static void updatePilot() {
56 storePilot();
57 ObjectContainer db=Db4o.openFile(YAPFILENAME);
58 try {
59 ObjectSet result=db.get(new Pilot("Michael Schumacher",10));
61 Pilot found=(Pilot)result.next();
62 found.addPoints(10);
63 db.set(found);
64 System.out.println("Added 10 points for "+found);
65 } finally {
66 db.close();
67 }
68 retrieveAllPilots();
69 }
70
72 public static void updatePilotWrong() {
73 storePilot();
74 ObjectContainer db=Db4o.openFile(YAPFILENAME);
75 try {
76 Pilot pilot = new Pilot("Michael Schumacher",10);
79 pilot.addPoints(10);
80 db.set(pilot);
81 System.out.println("Added 10 points for "+pilot);
82 } finally {
83 db.close();
84 }
85 retrieveAllPilots();
86 }
87
89 public static void deletePilot() {
90 storePilot();
91 ObjectContainer db=Db4o.openFile(YAPFILENAME);
92 try {
93 ObjectSet result=db.get(new Pilot("Michael Schumacher",10));
95 Pilot found=(Pilot)result.next();
96 db.delete(found);
97 System.out.println("Deleted "+found);
98 } finally {
99 db.close();
100 }
101 retrieveAllPilots();
102 }
103
105
106 public static void retrieveAllPilots() {
107 ObjectContainer db=Db4o.openFile(YAPFILENAME);
108 try {
109 Query query=db.query();
110 query.constrain(Pilot.class);
111 ObjectSet result=query.execute();
112 listResult(result);
113 } finally {
114 db.close();
115 }
116 }
117
119 public static void retrievePilotByName(ObjectContainer db) {
120 Query query=db.query();
121 query.constrain(Pilot.class);
122 query.descend("name").constrain("Michael Schumacher");
123 ObjectSet result=query.execute();
124 listResult(result);
125 }
126
128 public static void retrievePilotByExactPoints(
129 ObjectContainer db) {
130 Query query=db.query();
131 query.constrain(Pilot.class);
132 query.descend("points").constrain(new Integer (100));
133 ObjectSet result=query.execute();
134 listResult(result);
135 }
136
138 public static void retrieveByNegation(ObjectContainer db) {
139 Query query=db.query();
140 query.constrain(Pilot.class);
141 query.descend("name").constrain("Michael Schumacher").not();
142 ObjectSet result=query.execute();
143 listResult(result);
144 }
145
147 public static void retrieveByConjunction(ObjectContainer db) {
148 Query query=db.query();
149 query.constrain(Pilot.class);
150 Constraint constr=query.descend("name")
151 .constrain("Michael Schumacher");
152 query.descend("points")
153 .constrain(new Integer (99)).and(constr);
154 ObjectSet result=query.execute();
155 listResult(result);
156 }
157
159 public static void retrieveByDisjunction(ObjectContainer db) {
160 Query query=db.query();
161 query.constrain(Pilot.class);
162 Constraint constr=query.descend("name")
163 .constrain("Michael Schumacher");
164 query.descend("points")
165 .constrain(new Integer (99)).or(constr);
166 ObjectSet result=query.execute();
167 listResult(result);
168 }
169
171 public static void retrieveByComparison(ObjectContainer db) {
172 Query query=db.query();
173 query.constrain(Pilot.class);
174 query.descend("points")
175 .constrain(new Integer (99)).greater();
176 ObjectSet result=query.execute();
177 listResult(result);
178 }
179
181 public static void retrieveByDefaultFieldValue(
182 ObjectContainer db) {
183 Pilot somebody=new Pilot("Somebody else",0);
184 db.set(somebody);
185 Query query=db.query();
186 query.constrain(Pilot.class);
187 query.descend("points").constrain(new Integer (0));
188 ObjectSet result=query.execute();
189 listResult(result);
190 db.delete(somebody);
191 }
192
194 public static void retrieveSorted(ObjectContainer db) {
195 Query query=db.query();
196 query.constrain(Pilot.class);
197 query.descend("name").orderAscending();
198 ObjectSet result=query.execute();
199 listResult(result);
200 query.descend("name").orderDescending();
201 result=query.execute();
202 listResult(result);
203 }
204
206 public static void clearDatabase(ObjectContainer db) {
207 ObjectSet result=db.get(Pilot.class);
208 while(result.hasNext()) {
209 db.delete(result.next());
210 }
211 }
212
214 public static void listResult(ObjectSet result) {
215 System.out.println(result.size());
216 while(result.hasNext()) {
217 System.out.println(result.next());
218 }
219 }
220 }
222 |
Popular Tags |
Java API By Example, From Geeks To Geeks.