Use ormlite for persistence in Android

 

Android has built-in sqlite, but the common development language java is object-oriented, while the database is relational, every conversion between the two is very troublesome (I am not familiar with the SQL language ). Java Web development has a lot of orm frameworks, but it is troublesome to directly use them on Android. I tried to find the Android orm framework. To tell the truth, there are several more.

The implementation considerations are: androrm Official Website: http://androrm.the-pixelpla.net/to put it bluntly, I have no idea about this. I have two packages in total. One is the dependency package: Apache Commons-Lang (2.6) and the other is the main package: androrm. jar cannot be downloaded... next, let's take a look at the db4o Official Website: The ormlite official website was last seen by ghost: follow the Convention to create a Hello world Android project: HelloOrmLite

Add Folder: libs, copy the two required packages to it. Add reference

Create a model: Hello. java

package cn.sdx.model; import com.j256.ormlite.field.DatabaseField; public class Hello { @DatabaseField(generatedId = true) int id; @DatabaseField String word; public Hello() { } @Override public String toString() {   StringBuilder sb = new StringBuilder();   sb.append("id=").append(id);   sb.append(" ,word=").append(word);   return sb.toString(); } } 

@ DatabaseField declares that id is a database field, generatedId = true declares that id is auto-incrementing, and then overwrites toString () to add a DataHelper. java

Package cn. sdx. utils; import java. SQL. SQLException; import android. content. context; import android. database. sqlite. SQLiteDatabase; import android. util. log; import cn. sdx. model. hello; import com. j256.ormlite. android. apptools. ormLiteSqliteOpenHelper; import com. j256.ormlite. dao. dao; import com. j256.ormlite. support. connectionSource; import com. j256.ormlite. table. tableUtils; public class DataHelper extends OrmLiteSqliteOpenHelper {private static final String DATABASE_NAME = "HelloOrmlite. db "; private static final int DATABASE_VERSION = 1; private Dao <Hello, Integer> helloDao = null; public DataHelper (Context context) {super (context, DATABASE_NAME, null, DATABASE_VERSION) ;}@ Override public void onCreate (SQLiteDatabase db, ConnectionSource connectionSource) {try {TableUtils. createTable (connectionSource, Hello. class);} catch (SQLException e) {Log. e (DataHelper. class. getName (), "failed to create database", e); e. printStackTrace () ;}@ Override public void onUpgrade (SQLiteDatabase db, ConnectionSource connectionSource, int arg2, int arg3) {try {TableUtils. dropTable (connectionSource, Hello. class, true); onCreate (db, connectionSource);} catch (SQLException e) {Log. e (DataHelper. class. getName (), "failed to update database", e); e. printStackTrace () ;}@ Override public void close () {super. close (); helloDao = null;} public Dao <Hello, Integer> getHelloDataDao () throws SQLException {if (helloDao = null) {helloDao = getDao (Hello. class) ;}return helloDao ;}}

The following code adds TextViewHelloOrmliteActivity. java to the layout file:

Package cn. sdx; import java. SQL. SQLException; import java. util. list; import com. j256.ormlite. android. apptools. ormLiteBaseActivity; import com. j256.ormlite. dao. dao; import android. OS. bundle; import android. widget. textView; import cn. sdx. model. hello; import cn. sdx. utils. dataHelper; public class HelloOrmliteActivity extends OrmLiteBaseActivity <DataHelper> {/** Called when the activity is first created. * // @ Override public void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. main); TextView TV = (TextView) this. findViewById (R. id. output); try {Dao <Hello, Integer> helloDao = getHelper (). getHelloDataDao (); // Add data for (int I = 0; I <2; I ++) {Hello hello = new Hello ("Hello" + I); helloDao. create (hello);} TV. setText (TV. getText () + "\ n" + "added data"); // query the added data List <Hello> hellos = helloDao. queryForAll (); for (Hello h: hellos) {TV. setText (TV. getText () + "\ n" + h. toString ();} // Delete the first data helloDao. delete (hellos. get (0); TV. setText (TV. getText () + "\ n" + ""); // query the data again. hellos = helloDao. queryForAll (); for (Hello h: hellos) {TV. setText (TV. getText () + "\ n" + h. toString ();} // modify the data Hello h1 = hellos. get (0); h1.setWord ("this is modified data"); TV. setText (TV. getText () + "\ n" + "data modified"); helloDao. update (h1); // re-query the data hellos = helloDao. queryForAll (); for (Hello h: hellos) {TV. setText (TV. getText () + "\ n" + h. toString () ;}} catch (SQLException e) {// TODO Auto-generated catch block e. printStackTrace ();}}}

The above implementation of database operations related to addition, deletion, and modification, the following is the effect:

OrmLite has very powerful functions. The declaration of Model classes is very important. Foreign key constraints and non-empty checks all have relative solutions. Author: huangyunkun