Android ContentProvider Generator (acpg)
A tool to generate Android ContentProviders. It takes a set of entity (a.k.a "table") definitions as the input, and generates:
- a
ContentProvider
class - an
SQLiteOpenHelper
class - one
Columns
class per entity - one
Cursor
class per entity - one
ContentValues
class per entity - one
Selection
class per entity - one
Model
interface per entity - one
Bean
class per entity (optionally)
Usage
There are two possible ways to generate the code:
- as part of the build script (with a Gradle plugin)
- as a one-time step (using a command line tool)
The Gradle plugin is perhaps the 'cleaner' way in the sense that the generated code won't be part of the source (not checked into VCS). The configuration is declared inside the Gradle script which allows to update it easily.
Alternatively, a one-time generation can be done (typically at the beginning of the project.) The generated code is part of the source and checked into VCS: this allows you to modify it if you need to.
You can decide which option is the best for your project :)
Option 1: Gradle plugin
Add this to your app's build.gradle
:
buildscript {
dependencies {
classpath 'org.jraf:acpg-gradle-plugin:1.13.1'
}
}
apply plugin: 'org.jraf.acpg.gradleplugin'
(...)
// This is where you declare a few parameters used to generate the code
acpg {
// Where to find the entity files (see 'Entity files' below)
// Optional - default value: 'etc/acpg' in the root project
entitiesDir file('etc/acpg-entities')
// Java package in which all the code will be generated
providerJavaPackage 'com.example.app.provider'
// ContentProvider authority
// "${applicationId}" will be substituted by BuildConfig.APPLICATION_ID in the generated code
authority '${applicationId}.provider'
// Name of the provider class
providerClassName 'ExampleProvider'
// Name of the db file
databaseFileName 'example.db'
// Version of the db
databaseVersion 1
// Name of the SQLiteOpenHelper class
// Optional - default value: providerClassName + "SQLiteOpenHelper"
sqliteOpenHelperClassName 'ExampleSQLiteOpenHelper'
// Name of a subclass of BaseSQLiteOpenHelperCallbacks
// Optional - this allows you to get called when the db is opened/created/upgraded
sqliteOpenHelperCallbacksClassName 'ExampleSQLiteOpenHelperCallbacks'
// Whether to enable foreign keys support (see 'Advanced usage' below)
// Optional - default value: false
enableForeignKeys true
// Whether @Nullable/@NonNull annotations will be used in the generated code
// Optional - default value: false
useAnnotations true
// Whether support library classes are used or the Android SDK ones (e.g. CursorLoader)
// Optional - default value: false
useSupportLibrary true
// Whether to generate a 'Beans' class for each entity
// Optional - default value: true
generateBeans true
// Name of a boolean field in BuildConfig to enable/disable debug logging in the generated code
// Optional - default value: "DEBUG"
debugLogsFieldName 'LOG_DEBUG_PROVIDER'
// Version of the tool syntax (must be 4)
// The allows to break the build immediately if an incompatible version of the tool is used. Safety first!
// Optional - default value: 4
syntaxVersion 4
}
Option 2: Command line tool
The configuration is the same, except you declare it in a file named _config.json
in the same folder as the entity files.
Here is an example:
{
"syntaxVersion": 4,
"packageName": "com.example.app",
"providerJavaPackage": "com.example.app.provider",
"authority": "${applicationId}.provider",
"providerClassName": "ExampleProvider",
"databaseFileName": "example.db",
"databaseVersion": 1,
"sqliteOpenHelperClassName": "ExampleSQLiteOpenHelper",
"sqliteOpenHelperCallbacksClassName": "ExampleSQLiteOpenHelperCallbacks",
"enableForeignKeys": true,
"useAnnotations": true,
"useSupportLibrary": true,
"generateBeans": true,
"debugLogsFieldName": "LOG_DEBUG_PROVIDER"
}
About packageName
: this must be the same as the value of the package
attribute in your manifest. Not to be confused with the applicationId
(see https://developer.android.com/studio/build/application-id.html)
Get and run the tool
Download the acpg-cli-1.13.1.jar
file here: https://github.com/BoD/android-contentprovider-generator/releases/latest
java -jar acpg-cli-1.13.1.jar -i <input folder> -o <output folder>
- Input folder: where to find
_config.json
and your entity json files - Output folder: where the resulting files will be generated
Entity files
Create one file per entity, naming it <entity_name>.json
. Inside each file, declare your fields (a.k.a "columns") with a name and a type. You can also optionally declare a default value, an index flag, a documentation and a nullable flag.
Currently the type can be:
String
(SQLite type:TEXT
)Integer
(INTEGER
)Long
(INTEGER
)Float
(REAL
)Double
(REAL
)Boolean
(INTEGER
)Date
(INTEGER
)byte[]
(BLOB
)enum
(INTEGER
).
You can also optionally declare table constraints.
Here is a person.json
file as an example:
{
"documentation": "A human being which is part of a team.",
"fields": [
{
"documentation": "First name of this person. For instance, John.",
"name": "first_name",
"type": "String",
"defaultValue": "John"
},
{
"documentation": "Last name (a.k.a. Given name) of this person. For instance, Smith.",
"name": "last_name",
"type": "String",
"nullable": true,
"defaultValue": "Doe"
},
{
"name": "age",
"type": "Integer",
"index": true
},
{
"name": "gender",
"type": "enum",
"enumName": "Gender",
"enumValues": [
"MALE",
"FEMALE",
{"OTHER": "Value to use when neither male nor female"}
],
"nullable": false
}
],
"constraints": [
{
"name": "unique_name",
"definition": "UNIQUE (first_name, last_name) ON CONFLICT REPLACE"
}
],
"defaultOrder": "first_name, last_name, age DESC"
}
Notes:
- An
_id
primary key field is automatically (implicitly) declared for all entities. It must not be declared in the json file. nullable
is optional (true by default).- if
documentation
is present the value will be copied in Javadoc blocks in the generated code. - the
constraints
anddefaultOrder
sections are optional
A more comprehensive sample is available in the sample-app/etc/acpg folder.
You can have a look at the corresponding generated code in the etc/sample-generated-code folder.
By convention, you should name your entities and fields in lower case with words separated by '_', like in the example above.
The header.txt
file (optional)
If a header.txt
file is present, its contents will be inserted at the top of every generated file.
Use the generated files
- When querying a table, use the corresponding
Selection
class as shown in this example:
PersonSelection where = new PersonSelection();
where.firstName("John").or().age(42);
Cursor c = context.getContentResolver().query(where.uri(), projection,
where.sel(), where.args(), null);
- When using the results of a query, wrap the resulting
Cursor
in the corresponding wrapper class. You can then use the generated getters directly as shown in this example:
PersonCursor person = new PersonCursor(c);
String lastName = person.getLastName();
Long age = person.getAge();
- You can also conveniently combine these two facilities by using the
query
(ordelete
) method:
PersonSelection where = new PersonSelection();
where.firstName("John").or().age(42).orderByFirstName();
PersonCursor person = where.query(context);
person.moveToNext();
String lastName = person.getLastName();
Long age = person.getAge();
or, use a CursorLoader
:
where.getCursorLoader(context);
- When updating or inserting into a table, use the corresponding
ContentValues
class as shown in this example:
PersonContentValues values = new PersonContentValues();
values.putFirstName("John").putAge(42);
context.getContentResolver().update(values.uri(), values.values(), null, null);
or
values.insert(context);
Advanced usage
Foreign key / joins
There is limited support for foreign keys and joins. Here is an example of the syntax:
{
"fields": [
{
"name": "main_team_id",
"type": "Long",
"nullable": false,
"foreignKey": {
"table": "team",
"onDelete": "CASCADE"
}
},
{
"name": "first_name",
"type": "String",
"nullable": false
},
(...)
}
In this example, the field main_team_id
is a foreign key referencing the primary key of the team
table.
- The appropriate
FOREIGN KEY
SQL constraint is generated (ifenableForeignKeys
is set totrue
in_config.json
). - The
team
table will be automatically joined when querying theperson
table[1]
. - Getters for
team
columns are generated in thePersonCursor
wrapper. - Of course if
team
has foreign keys they will also be handled (and recursively).
[1]
A table is automatically joined if at least one of its columns is included in the projection. If the projection is null
(i.e. all columns), all the tables are joined. Caution: you should be extra careful when using a null
projection with joins because you will get several columns named _id
in the results!
Limitations
- Foreign keys always reference the
_id
column (the implicit primary key of all tables) and thus must always be of typeLong
- by design. - Only one foreign key to a particular table is allowed per table. In the example above only one column in
person
can point toteam
. - Loops (i.e. A has a foreign key to B and B has a foreign key to A) aren't detected. The generator will infinitely loop if they exist.
- Cases such as "A has a FK to B, B has a FK to C, A has a FK to C" generate ambiguities in the queries, because C columns appear twice. In the sample app you can see an example of how to deal with this case, using prefixes and aliases (SQL's
AS
keyword).
Sample
A sample is available in the sample-app folder, with the entities in sample-app/etc/acpg.
You can have a look at the corresponding generated code in the etc/sample-generated-code folder.
Here is the table shema of the sample:
Building
This is a Gradle project.
./gradlew install
to 'install' the Gradle plugin to your local maven repo
./gradlew shadowJar
to build the cli tool
Similar tools
Here is a list of other tools that try to tackle the same problem.
I did not have the chance to try them out.
- https://github.com/SimonVT/schematic
- https://github.com/TimotheeJeannin/ProviGen
- http://triple-t.github.io/simpleprovider/
- https://github.com/foxykeep/ContentProviderCodeGenerator
- https://code.google.com/p/mdsd-android-content-provider/
- https://github.com/hamsterksu/Android-AnnotatedSQL
- http://robotoworks.com/mechanoid/doc/db/api.html
- https://github.com/robUx4/android-contentprovider-generator (a fork of this project that generates more code)
- https://github.com/novoda/sqlite-analyzer (based on sql statements, not json)
- https://github.com/ckurtm/simple-sql-provider
Licence
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.
Just to be absolutely clear, this license applies to this program itself, not to the source it will generate!