Android usage summary database GreenDao

A, GreenDao introduction

GreenDAO is an open source Android ORM ( "Object / Relational Mapping"), by ORM (referred to as "object / relational mapping"), it saves us time database development process!

By GreenDao, we can more quickly operate the database, we can use a simple object-oriented API to store, update, delete, and query Java objects.

GreenDao advantages and disadvantages?

1. High performance

2. Easy to use powerful API, covering relationships and connections

3. The minimum memory consumption

4. Library size (<100KB) constructed to hold a lower limit time and avoid Method 65k

5. Database Encryption: greenDAO support SQLCipher, to ensure the security of user data;

GreenDao core classes

GreenDao has three core classes: namely DaoMaster, DaoSession, XXXDao, three classes will be created automatically, without the need to write your own creation!

• DaoMaster :: DaoMaster database objects and manage DAO class-specific pattern. It has a static method to create a table or delete them. Its interior is class OpenHelper and DevOpenHelper SQLiteOpenHelper realize that they create patterns in the SQLite database.
• DaoSession: All available DAO object management specific pattern, you can use one getter method to get the object. DaoSession also provides some general persistence methods, such as the entity is inserted, load, update, delete and refresh.
• XXXDao: Data Access Objects (DAO) and persistent query entity. For each entity, greenDAO generated DAO. It has more than DaoSession persistence method.
• Entities: be persistent object. Typically, the database entity object representative of a line using the standard Java properties (e.g., a POJO or JavaBean).

Two, GreenDao use

1. Import Gradle widget code generation and Dao

To use GreenDao in the Android project, you need to add plug-ins and add GreenDao GreenDao Gradle library:

a). Import widget

// 在 Project的build.gradle 文件中添加:
buildscript {
    repositories {
        jcenter()
        mavenCentral() // add repository
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.2'
        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // add plugin
    }
}

b). configure its dependencies

// 在 Moudle:app的  build.gradle 文件中添加:
apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao' // apply plugin
 
dependencies {
    implementation 'org.greenrobot:greendao:3.2.2' // add library
}

c). the configuration database information

{greendao 
    schemaVersion . 1 // database version number 
    daoPackage 'com.renhui.testapp.functions.database.greenDao.db' // set DaoMaster, DaoSession, Dao package names 
    targetGenDir 'src.main.java' // set DaoMaster, DaoSession, Dao directory, note that with this path. Do not use / 
    generateTests to false // set true to automatically generate test unit. 
    targetGenDirTests 'the src / main / Java' // should be stored substantially catalog generation unit tests. The default is src / androidTest / java. 
}
 

Configuration is complete, use Build> Make Project In Android Studio, rewrite build the project, GreenDao the integration is complete!

2. Create a storage object entity classes

GreenDao using only data stored in the storing annotation data previously declared class @Entity let GreenDao for generating the necessary code:

@Entity
 public  class Student { 
    the @Id (AUTOINCREMENT = to true ) 
    Long the above mentioned id; 
    @Unique 
    int studentNo; // Student ID 
    int Age; // Age 
    String Cellphone; // phone number 
    String Sex; // gender 
    String name; // Name 
    address String; // home address 
    String schoolName; // school name 
    String grade; // What grade 
    ...... getter and setter and constructor Method, ...... 
    }

3. GreenDao initialization

We can maintain a global conversation in the Application. We initialize the database operations in Applicaiton: =

　　/**
     * 初始化GreenDao,直接在Application中进行初始化操作
     */
    private void initGreenDao() {
        DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(this, "aserbao.db");
        SQLiteDatabase db = helper.getWritableDatabase();
        DaoMaster daoMaster = new DaoMaster(db);
        daoSession = daoMaster.newSession();
    }
    
    private DaoSession daoSession;
    public DaoSession getDaoSession() {
        return daoSession;
    }

After initialization is complete again rebuild what the project will find a set of directories targetGenDir generate three types of documents, this is GreenDao generated automatically! Description of the database has been connected, we just need to be followed by additions and deletions to change search the database operation on the line.

4. GreenDao implemented CRUD

1. increase

insert () Insert data

@Override
public void insertData(Thing s) {
    DaoSession daoSession = ((AserbaoApplication) getApplication()).getDaoSession();
    for (int i = 0; i < 1000; i++) {
        Student student = new Student();
        student.setStudentNo(i);
        int age = mRandom.nextInt(10) + 10;
        student.setAge(age);
        student.setTelPhone(RandomValue.getTel());
        String chineseName = RandomValue.getChineseName();
        student.setName(chineseName);
        if (i % 2 == 0) {
            student.setSex("男");
        } else {
            student.setSex("女");
        }
        student.setAddress(RandomValue.getRoad());
        student.setGrade(String.valueOf(age % 10) + "年纪");
        student.setSchoolName(RandomValue.getSchoolName());
        daoSession.insert(student);
    }
} 

insertOrReplace () data exists is replaced, the data does not exist insert

@Override
public void insertData(Thing s) {
    DaoSession daoSession = ((AserbaoApplication) getApplication()).getDaoSession();
    for (int i = 0; i < 1000; i++) {
        Student student = new Student();
        student.setStudentNo(i);
        int age = mRandom.nextInt(10) + 10;
        student.setAge(age);
        student.setTelPhone(RandomValue.getTel());
        String chineseName = RandomValue.getChineseName();
        student.setName(chineseName);
        if (i % 2 == 0) {
            student.setSex ( "M" ); 
        } the else { 
            student.setSex ( "F" ); 
        } 
        student.setAddress (RandomValue.getRoad ()); 
        student.setGrade (String.valueOf (Age % 10) + "old" ) ; 
        student.setSchoolName (RandomValue.getSchoolName ()); 
        daoSession.insertOrReplace (Student); // insert or replace 
    } 
} 

2. deleted

There are two ways to delete: delete () and deleteAll (); respectively, and delete all delete individual.

 @Override
 public void deleteData(Student s) {
     DaoSession daoSession = ((AserbaoApplication) getApplication()).getDaoSession();
     daoSession.delete(s);
 }

 @Override
 public void deleteAll() {
     DaoSession daoSession = ((AserbaoApplication) getApplication()).getDaoSession();
     daoSession.deleteAll(Student.class);
 }

3. change

Be modified by the update:

@Override
public void updataData(Student s) {
    DaoSession daoSession = ((AserbaoApplication) getApplication()).getDaoSession();
    daoSession.update(s);
}

4. Charles

The method of inquiry are:

• loadAll (): Query all data.
• queryRaw (): according to the conditions query.
• queryBuilder (): easily create queries, followed by a detailed explanation.

public List queryAll() {
    List<Student> students = daoSession.loadAll(Student.class);
    return students;
}

@Override
public void queryData(String s) {
    List<Student> students = daoSession.queryRaw(Student.class, " where id = ?", s);
    mDataBaseAdapter.addNewStudentData(students);
}

 

 

Reference: https://www.jianshu.com/p/53083f782ea2