Realm 数据库取代sqlite？

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Realm 是一个orm数据库,适用于android,ios；据说速度超越sqlite(这一点我将在后面有实例验证),还支持json,加密支持

第一步:

compile 'io.realm:realm-android:0.84.1'

第二步:

创建模型:javaBean 必须标准化,字段要私有，要有get set方法，toString方法都不可以有,有严格要求，果真是牺牲自由行来换取速度

package com.xuan.realm.bean;import io.realm.RealmObject;/** * @author xuanyouwu * @email xuanyouwu@163.com * @time 2016-05-05 10:02 */public class User extends RealmObject {    private String name;    private int age;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}

第三步:创建一个Realm对象

mRealm = Realm.getInstance(this);

保存对象:

  User user = new User();        user.setName("hhh");        user.setAge(25);        mRealm.beginTransaction();        mRealm.copyToRealm(user);        mRealm.commitTransaction();

查询对象:

  RealmResults<User> all = mRealm.where(User.class).findAll();

全部代码:

package com.xuan.realm;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import com.xuan.realm.bean.User;import com.xuan.realm.utils.LogUtils;import io.realm.Realm;import io.realm.RealmResults;public class MainActivity extends AppCompatActivity {    Realm mRealm;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mRealm = Realm.getInstance(this);    }    public void onSave(View v) {        User user = new User();        user.setName("hhh");        user.setAge(25);        mRealm.beginTransaction();        mRealm.copyToRealm(user);        mRealm.commitTransaction();    }    public void onQuery(View v) {        RealmResults<User> all = mRealm.where(User.class).findAll();        LogUtils.d("----->query:" + all);    }}

</pre><pre code_snippet_id="1672753" snippet_file_name="blog_20160505_4_2130749" name="code" class="java">对比:插入100次:

<pre name="code" class="java"> long startTime = System.currentTimeMillis();                for (int i = 0; i < 100; i++) {                    studentDao.insertData(new Student("name:" + SystemClock.elapsedRealtime(), new Random().nextInt(100)));                }                long endTime = System.currentTimeMillis();                Log.d("-------->sqlite 原生:耗时1:", "" + (endTime - startTime));                long startTime1 = System.currentTimeMillis();                for (int i = 0; i < 100; i++) {                    Student1 student1 = new Student1();                    student1.setName("name:" + SystemClock.elapsedRealtime());                    student1.setAge(new Random().nextInt(100));                    daoSession.insertOrReplace(student1);                }                long endTime1 = System.currentTimeMillis();                Log.d("-------->greendao 耗时2:", "" + (endTime1 - startTime1));                long startTime2 = System.currentTimeMillis();                for (int i = 0; i < 100; i++) {                    StudentReleam student1 = new StudentReleam();                    student1.setName("name:" + SystemClock.elapsedRealtime());                    student1.setAge(new Random().nextInt(100));                    mRealm.beginTransaction();                    mRealm.copyToRealm(student1);                    mRealm.commitTransaction();                }                long endTime2 = System.currentTimeMillis();                Log.d("-------->Realm 耗时3:", "" + (endTime2 - startTime2));

05-05 03:32:49.561 11993-11993/com.xuan.greendaotest D/-------->sqlite 原生:耗时1:: 60505-05 03:32:50.246 11993-11993/com.xuan.greendaotest D/-------->greendao 耗时2:: 68505-05 03:32:50.677 11993-11993/com.xuan.greendaotest D/-------->Realm 耗时3:: 431

查询100次总时间:

    //查询100次                        int totalTime = 0;                        for (int i = 0; i < 100; i++) {                            long startTime = System.currentTimeMillis();                            String sql = String.format("select  sum(%s) from %s", "age", "student");                            Cursor cursor = studentDao.helper.getWritableDatabase().rawQuery(sql, null);                            int sumAge = 0;                            if (cursor != null && cursor.moveToFirst()) {                                sumAge = cursor.getInt(0);                            }                            long endTime = System.currentTimeMillis();                            totalTime += (endTime - startTime);                        }                        Log.d("-------->sqlite 原生:耗时1:", "" + totalTime);                        int totalTime1 = 0;                        for (int j = 0; j < 100; j++) {                            long startTime1 = System.currentTimeMillis();                      /*      String sql = String.format("select  sum(%s) from %s", "AGE", "STUDENT1");                            Cursor cursor = daoSession.getDatabase().rawQuery(sql, null);                            int sumAge1 = 0;                            if (cursor != null && cursor.moveToFirst()) {                                sumAge1 = cursor.getInt(0);                            }*/                            List<Student1> student1s = daoSession.getStudent1Dao().loadAll();                            int sumAge1 = 0;                            if (student1s != null) {                                for (int i = 0; i < student1s.size(); i++) {                                    Student1 student1 = student1s.get(i);                                    if (student1 == null) continue;                                    sumAge1 += student1.getAge();                                }                            }                            long endTime1 = System.currentTimeMillis();                            totalTime1 += (endTime1 - startTime1);                        }                        Log.d("------->greendao 耗时2:", "" + totalTime1);                        int totalTime2 = 0;                        for (int j = 0; j < 100; j++) {                            long startTime2 = System.currentTimeMillis();                            int sumAge2 = 0;                            RealmResults<StudentReleam> all = mRealm.where(StudentReleam.class).findAll();                            if (all != null) {                                for (int i = 0; i < 100; i++) {                                    StudentReleam student1 = all.get(i);                                    if (student1 == null) continue;                                    sumAge2 += student1.getAge();                                }                            }                            long endTime2 = System.currentTimeMillis();                            totalTime2 += (endTime2 - startTime2);                        }                        Log.d("------->realm 耗时3:", "" + totalTime2);

结果:

05-05 03:36:06.226 11993-11993/com.xuan.greendaotest D/-------->sqlite 原生:耗时1:: 1052
05-05 03:36:06.769 11993-11993/com.xuan.greendaotest D/------->greendao 耗时2:: 543
05-05 03:36:07.977 11993-11993/com.xuan.greendaotest D/------->realm 耗时3:: 1208

总结:插入速度 realm>sqlite>greendao

查询速度:sqlite约等于greendao>realm

sqlite 有时候不稳定,几乎和greendao 持平,realm耗时比较稳定，但是几乎是前者的2倍时间

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