(一)附录1简介了Android Room的基本使用。在附录1例子中，User对象元素均为普通的Java基本数据类型，但是实际的开发中，通常建立的持久化存储对象复杂，且通常是结构化的Java对象，互相之间存在引用或者内嵌关系。

Android Room支持数据库表Java对象通过注解符@Embedded内嵌一个Java对象。这样就像过去的ORM数据库一样，比如构造一个名为Info的Java对象，作为一个成员变量添加到User里面：

package zhangphil.demo;

import android.arch.persistence.room.ColumnInfo;

import android.arch.persistence.room.Embedded;

import android.arch.persistence.room.Entity;

import android.arch.persistence.room.PrimaryKey;

/**

* Created by Phil on 2017/11/22.

*/

@Entity(tableName = "user_table")

public class User {

@PrimaryKey(autoGenerate = true)

public int userId;

@ColumnInfo(name = "userName")

public String name;

@ColumnInfo(name = "userAge")

public int age;

@ColumnInfo(name = "updateTime")

public long updateTime;

@Embedded

public Info info;

}

(二)Info对象本身也是一个Android Room的@Entity。也有自己的列名和主键等完整的Android Room数据表要素，Info.java：

package zhangphil.demo;

import android.arch.persistence.room.ColumnInfo;

import android.arch.persistence.room.Entity;

import android.arch.persistence.room.PrimaryKey;

/**

* Created by Phil on 2017/11/23.

*/

@Entity(tableName = "info_table")

public class Info {

@PrimaryKey(autoGenerate = true)

public int infoId;

@ColumnInfo(name = "blog")

public String blog;

@ColumnInfo(name = "content")

public String content;

}

(三)需要注意的是，通过Android Room的@Embedded符号内嵌的数据表，列表名将自动二次添加到“宿主”对象中。本例是User钟内嵌了Info，那么User数据库表user_table中将会被Android Room自动添加Info里面的列名字段。User的user_table中原有userId，name，age，updateTime四列，由于@Embedded了Info，那么Info里面的blog，content将会自动添加到User数据表中。但是Info的主键infoId将在User中被忽略不再被作为主键。

(四)写一个MainActivity.java测试：

package zhangphil.demo;

import android.arch.persistence.room.Room;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import java.util.List;

public class MainActivity extends AppCompatActivity {

private String TAG = "输出";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

new Thread(new Runnable() {

@Override

public void run() {

databaseOperation();

}

}).start();

}

private void databaseOperation() {

UserDatabase mUserDatabase = Room.databaseBuilder(getApplicationContext(), UserDatabase.class, "users").build();

UserDao mUserDao = mUserDatabase.getUserDao();

//写数据库

writeUserDatabase(mUserDao, "zhangphil", 18);

readDatabase(mUserDao);

//关闭数据库

mUserDatabase.close();

}

private void readDatabase(UserDao dao) {

Log.d(TAG, "读数据库...");

List users = dao.getAllUsers();

for (User u : users) {

Log.d(TAG, u.userId + "," + u.name + "," + u.age + ","+u.info.blog+","+u.info.content);

}

Log.d(TAG, "读数据库完毕.");

}

private void writeUserDatabase(UserDao dao, String name, int age) {

Info info = new Info();

info.blog = "http://blog.csdn.net/zhangphil";

info.content = "Android";

User user = new User();

user.name = name;

user.age = age;

user.updateTime = System.currentTimeMillis();

user.info = info;

dao.insertUser(user);

}

}

代码运行结果，logcat输出：

11-24 09:20:00.716 30805-30851/zhangphil.demo D/输出: 读数据库...

11-24 09:20:00.723 30805-30851/zhangphil.demo D/输出: 1,zhangphil,18,http://blog.csdn.net/zhangphil,Android

11-24 09:20:00.723 30805-30851/zhangphil.demo D/输出: 读数据库完毕.