上學的時候就聽老師說過有對象數據庫。
但是我所接觸的數據庫都是關系型數據庫mysql，oracle，ms sql server，或是db2.
最近在ibm development work上看到一個名為db4o的對象數據。
才看第一章，學過Java的都應該很容易理解的。
確實它真的很簡單。
看起來似乎就像是在一個Java的操作，而並非如我們所以為的那樣的想關系型數據庫中操作一樣。
如果有興趣的話，大家也可以去看看。
不過，文章作者也對db4o的一些缺點進行了列舉。
自己並沒有進行很深入的學習。
只是對其感興趣罷了。
或許對系數據庫可能讓我們進入一個新的世界。
1 public class Person
2 {
3 public Person()
4 { }
5 public Person(String firstName, String lastName, int age)
6 {
7 this.firstName = firstName;
8 this.lastName = lastName;
9 this.age = age;
10 }
11
12 public String getFirstName() { return firstName; }
13 public void setFirstName(String value) { firstName = value; }
14
15 public String getLastName() { return lastName; }
16 public void setLastName(String value) { lastName = value; }
17
18 public int getAge() { return age; }
19 public void setAge(int value) { age = value; }
20
21 public String toString()
22 {
23 return
24 "[Person: " +
25 "firstName = " + firstName + " " +
26 "lastName = " + lastName + " " +
27 "age = " + age +
28 "]";
29 }
30
31 public boolean equals(Object rhs)
32 {
33 if (rhs == this)
34 return true;
35
36 if (!(rhs instanceof Person))
37 return false;
38
39 Person other = (Person)rhs;
40 return (this.firstName.equals(other.firstName) &&
41 this.lastName.equals(other.lastName) &&
42 this.age == other.age);
43 }
44
45 private String firstName;
46 private String lastName;
47 private int age;
48 }
49
數據庫的insert
1
2 import com.tedneward.model.*;
3
4 public class Hellodb4o
5 {
6 public static void main(String[] args)
7 throws Exception
8 {
9 ObjectContainer db = null;
10 try
11 {
12 db = Db4o.openFile("persons.data");
13
14 Person brian = new Person("Brian", "Goetz", 39);
15
16 db.set(brian);
17 db.commit();
18 }
19 finally
20 {
21 if (db != null)
22 db.close();
23 }
24 }
25 }
26
或是用另外的一種方法進行insert操作。
1 public class Hellodb4o
2 {
3 public static void main(String[] args)
4 throws Exception
5 {
6 ObjectContainer db = null;
7 try
8 {
9 db = Db4o.openFile("persons.data");
10
11 Person brian = new Person("Brian", "Goetz", 39);
12 Person jason = new Person("Jason", "Hunter", 35);
13 Person clinton = new Person("Brian", "Sletten", 38);
14 Person david = new Person("David", "Geary", 55);
15 Person glenn = new Person("Glenn", "Vanderberg", 40);
16 Person neal = new Person("Neal", "Ford", 39);
17
18 db.set(brian);
19 db.set(jason);
20 db.set(clinton);
21 db.set(david);
22 db.set(glenn);
23 db.set(neal);
24
25 db.commit();
26
27 // Find all the Brians
28 ObjectSet brians = db.get(new Person("Brian", null, 0));
29 while (brians.hasNext())
30 System.out.println(brians.next());
31 }
32 finally
33 {
34 if (db != null)
35 db.close();
36 }
37 }
38 }
39
詳細介紹請參看ibm的學習文檔。
http://www.ibm.com/developerworks/cn/java/jdb4o/?ca=j-h
