android NoSql数据库io.paperdb:paperdb使用方法

Add dependency

compile 'io.paperdb:paperdb:2.5'

Initialize
Paper

Should be initialized one time in onCreate() in Application or Activity.

Paper.init(context);

It's OK to call it in UI thread. All other methods should be used in background.

Save

Save any data objects, Map, List, HashMap etc. including all the internal data hierarchy. Paper creates separate data file for each key.

Paper.book().write("city", "Lund"); // Object
Paper.book().write("task-queue", queue); // LinkedList
Paper.book().write("countries", countryCodeMap); // HashMap etc.

Read

Read data objects, the instantiated class is exactly the one used to save data. Limited changes to the class structure are handled automatically. See Handle
data class changes.

String city = Paper.book().read("city");
LinkedList queue = Paper.book().read("task-queue");
HashMap countryCodeMap = Paper.book().read("countries");

Use default values if object doesn't exist in the storage.

String city = Paper.book().read("city", "Kyiv");
LinkedList queue = Paper.book().read("task-queue", new LinkedList());
HashMap countryCodeMap = Paper.book().read("countries", new HashMap());

Delete

Delete data for one key.

Paper.book().delete("countries");

Completely destroys Paper storage. Requires to call 

Paper.init()

 before usage.

Paper.book().destroy();

Use
custom book

You can create custom Book with separate storage using

Paper.book("custom-book")...;

Each book is located in separate file folder.

Get
all keys

Returns all keys for objects in the book.

List<String> allKeys = Paper.book().getAllKeys();

Handle
data structure changes

Class fields which has been removed will be ignored on restore and new fields will have their default values. For example, if you have following data class saved in Paper storage:

class Volcano {
public String name;
public boolean isActive;
}

And then you realized you need to change the class like:

class Volcano {
public String name;
// public boolean isActive; removed field
public Location location; // New field
}

Then on restore the isActive field will be ignored and new location field will have its default value null.

Exclude
fields

Use transient keyword for fields which you want to exclude from saving process.

public transient String tempId = "default"; // Won't be saved

Proguard
config

Keep your data classes from modification by Proguard:

-keep class your.app.data.model.** { *; }

also you can implement Serializable for all your data classes and keep all of them using:

-keep class * implements java.io.Serializable { *; }

How
it works

Paper is based on the following assumptions:
Datasets on mobile devices are small and usually don't have relations in between;
Random file access on flash storage is very fast;

Paper saves each object for given key in a separate file and every write/read operations write/read the whole file.

The Kryo is used for object graph serialization and to provide data compatibility support.

Benchmark
results

Running Benchmark on Nexus 4, in ms:

Benchmark	Paper	Hawk	sqlite
Read/write 500 contacts	187	447
Write 500 contacts	108	221
Read 500 contacts	79	155

Limitations

Circular references are not supported

Apps
using Paper

AppDialer – Paper initially has been developed as internal lib to
reduce start up time for AppDialer. Currently AppDialer has the best start up time in its class. And simple no-sql-pain data storage layer like a bonus.

License

Copyright 2015 Aleksey Masny

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 http://www.apache.org/licenses/LICENSE-2.0 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.