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gerrit-public.fairphone.software / platform / external / jackson-core / f440fa0a38f69ca378f8e428cff016fa7028e1a9
commitf440fa0a38f69ca378f8e428cff016fa7028e1a9[log] [tgz]
authorBen Gertzfield <bgertzfield@gmail.com>Thu Jan 03 16:38:28 2013 -0800
committerBen Gertzfield <bgertzfield@gmail.com>Thu Jan 03 16:57:00 2013 -0800
tree4b83a563abceb8bb9bf1bcac8b2ed60820507e62
parentb3dfdea27efc5c309deda8e4404c4b9aa9a9c4ee [diff]
VersionUtil: Improve Android memory usage

The Android runtime implements Class.getResourceAsStream() with a very
memory-intensive cache, which holds the entire contents of the class's
.jar in memory.

A large Android app that uses Jackson will consume double the memory
today. Since memory is very tight on most Android devices, this diff
adds an alternative method to get version info for a package.

In specific, we now generate a class
com.fasterxml.jackson.core.json.PackageVersion at compile time.  At
run time, VersionUtil now checks the class's package to see if there's
a class named 'PackageVersion', and if so, reads its 'VERSION' static
field for the Version data for the package.  (If not, we still use
the existing VERSION.txt resource code as a fallback.)

I have separate patches for jackson-databind and
jackson-datatype-guava; it's easy to apply to other packages as well.

This is a nice performance improvement as well; we no longer incur all
the overhead of causing the runtime to open and cache the .jar
(unzipping it, etc.) just to read the VERSION.txt resource.

If the PackageVersion class doesn't exist, we'll of course fall back to the
existing test to get version info.

I confirmed using the Eclipse Memory Analyzer[1] that memory usage for
a large app I work on was reduced by about 5 MB with this fix (as well
as the jackson-databind and jackson-datatype-guava fixes).

Unit tests included.

[1] http://www.eclipse.org/mat/
6 files changed
tree: 4b83a563abceb8bb9bf1bcac8b2ed60820507e62
  1. release-notes/
  2. src/
  3. .gitignore
  4. create-test-report.sh
  5. pom.xml
  6. README.md
README.md

Overview

This project contains core core low-level incremental ("streaming") parser and generator abstractions used by Jackson Data Processor. It also includes the default implementation of handler types (parser, generator) that handle JSON format. The core abstractions are not JSON specific, although naming does contain 'JSON' in many places, due to historical reasons. Only packages that specifically contain word 'json' are JSON-specific.

This package is the base on which Jackson data-binding package builds on.

Alternate data format implementations (like Smile (binary JSON), XML and CSV) also build on this base package, implementing the core interfaces, making it possible to use standard data-binding package regardless of underlying data format.

Project contains versions 2.0 and above: source code for earlier (1.x) versions is available from Codehaus SVN repository.

Build Status

Differences from Jackson 1.x

Project contains versions 2.0 and above: source code for earlier (1.x) versions is available from Codehaus SVN repository

Note that the main differences compared to 1.0 core jar are:

  • Maven build instead of Ant
  • Annotations carved out to a separate package (that this package depends on)
  • Java package is now com.fasterxml.jackson.core (instead of org.codehaus.jackson)

Get it!

Maven

Functionality of this package is contained in Java package com.fasterxml.jackson.core.

To use the package, you need to use following Maven dependency:

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-core</artifactId>
  <version>2.1.1</version>
</dependency>

or download jars from Maven repository or Download page. Core jar is a functional OSGi bundle, with proper import/export declarations.

Package has no external dependencies, except for testing (which uses JUnit).

Non-Maven

For non-Maven use cases, you download jars from Central Maven repository or Download page.

Core jar is also a functional OSGi bundle, with proper import/export declarations, so it can be use on OSGi container as is.

Use it!

General

Usage typically starts with creation of a reusable (and thread-safe, once configured) JsonFactory instance:

JsonFactory factory = new JsonFactory();
// configure, if necessary:
factory.enable(JsonParser.Feature.ALLOW_COMMENTS);

Alternatively, you have a ObjectMapper (from Jackson Databind package) handy; if so, you can do:

JsonFactory factory = objectMapper.getJsonFactory();

Usage, simple reading

All reading is by using JsonParser (or its sub-classes, in case of data formats other than JSON), instance of which is constructed by JsonFactory:

(TO BE WRITTEN)

Usage, simple writing

All writing is by using JsonGenerator (or its sub-classes, in case of data formats other than JSON), instance of which is constructed by JsonFactory:

(TO BE WRITTEN)

Further reading

Project-specific documentation:

Related: