Db4o-based Java Map

Java map is the most commonly used container interface. It stores data through flexible key/value structures. Because map is easy to use, many engineers prefer to use map to store data in large quantities. However, map data is stored in the memory, and a large amount of data is stored in the memory, which is not only a worry about slow memory traversal in the Java system, but also a system memory overflow. To solve this problem, we re-use db4o to implement the map interface, and use the efficient physical storage feature of db4o objects to reduce the memory pressure of Java. The logical diagram is as follows:


Operation example

Package COM. shine. framework. db4o. example; import Java. util. hashmap; import Java. util. map; import COM. shine. framework. db4o. util. db4omap; public class db4omapexample {/*** @ Param ARGs */public static void main (string [] ARGs) {/** ============= Simple Object Storage Service =============== */db4omap <string, object> map = new db4omap <string, Object> (true); // Add data system. out. println (map. put ("key1", "value1"); system. out. println (map. put ("key1", "value2"); system. out. println (map. put ("key1", "value3"); system. out. println (map. put ("key1", "value4"); system. out. println (map. put ("key2", "value2"); system. out. println (map. put ("key3", "value3"); system. out. println (map. put ("key4", "value4"); // check the data system. out. println (map. containskey ("key1"); system. out. println (map. containsvalue ("value1"); system. out. println (map. isempty (); // obtain a single data entry system. out. println (map. get ("key2"); // delete a single data entry system. out. println (map. remove ("key1"); system. out. println (map. remove ("key4", "value4"); // deletes all data maps. removeall ("key2"); // query all data for (Object OBJ: map. getall () {system. out. println (OBJ);} // traverses all keys for (string key: map. keyset () {system. out. println (key);} // traverses all values for (object Value: map. values () {system. out. println (value);} // traverses all key-value pairs for (map. entry <string, Object> entry: map. entryset () {system. out. println (entry. getkey () + ":" + entry. getvalue ();} // clear all data map. clear (); // query the total number of system. out. println (map. size (); // release the resource map. destroy ();/** ============= advanced Object Storage Service =============== */db4omap <string, map <string, string> MAP2 = new db4omap <string, Map <string, string> (); // Add Data Map <string, string> data1 = new hashmap <string, string> (); data1.put ("data1.key1", "data1.value1"); data1.put ("data1.key2", "data1.value2"); Map <string, string> data2 = new hashmap <string, string> (); data2.put ("data2.key1", "data2.value1"); data2.put ("data2.key2", "data2.value2"); Map <string, string> data3 = new hashmap <string, string> (); data3.put ("data3.key1", "data3.value1"); Map <string, string> data4 = new hashmap <string, string> (); data4.put ("data4.key1", "data4.value1"); data4.put ("data4.key2", "data4.value1"); data4.put ("data4.key3", "data4.value1 "); map2.put ("map1", data1); map2.put ("MAP2", data2); map2.put ("map3", data3); map2.put ("map3", data4 ); // check the data system. out. println (map2.containskey ("map1"); system. out. println (map2.containsvalue (data1); // obtain a single data entry system. out. println (map2.get ("map1"); // remove a single data entry system. out. println (map2.remove ("MAP2"); // remove the specified key-value pair system. out. println (map2.remove ("map1", data1); // traverses all keys for (string key: map2.keyset () {system. out. println (key);} // traverses all key-value pairs for (map. entry <string, Map <string, string> entry: map2.entryset () {system. out. println (entry. getkey () + ":" + entry. getvalue ();} // traverse all data for (Map <string, string> datas: map2.getall () {for (map. entry <string, string> entry: datas. entryset () {system. out. println (entry. getkey () + ":" + entry. getvalue () ;}/// clear all data map2.clear (); // query the total number of system. out. println (map2.size (); map2.destroy ();}}

Thanks to my colleague qun1988@gmail.com, if you have any problems, you can contact him.
SVN address: http://code.google.com/p/ken-javaframeword/source/browse/trunk/JavaFramework2.5/src/com/shine/framework/DB4o/example/DB4oMapExample.java
Interested in javaframework2.5 this SVN downloading http://code.google.com/p/ken-javaframeword/source/browse/trunk/JavaFramework2.5