Transforming a non-OSGi JAR file into an Standard OSGi Bundle

    转换一个非OSGi Bundle成为一个标准的OSGi Bundle一般要实现下面几个问题：

1. IMPORTING PACKAGES

    The following guidelines is adopted when handle the Import-Package header:

    ■ Import the packages that the library or framework uses, and don’t import unused

       packages, which  would tie the bundle to unnecessary dependencies.
    ■ Specify the version of the packages, so the library or framework won’t use classes

       that it isn’t meant to use, which could lead to unexpected behavior.
    ■ Specify the difference between mandatory and optional dependencies by using the

       resolution directive.

    示例：

    Import-Package: org.hibernate;version="[3.2.6.ga,4.0.0)";resolution:=optional,
    org.hibernate.cache;version="[3.2.6.ga,4.0.0)";resolution:=optional,org.hibernate.cfg;

    version="[3.2.6.ga,4.0.0)";resolution:=optional,
    (...)
    com.ibatis.common.util;version="[2.3.0.677, 3.0.0)";resolution:=optional,
    com.ibatis.common.xml;version="[2.3.0.677, 3.0.0)";resolution:=optional,
    com.ibatis.sqlmap.client;version="[2.3.0.677, 3.0.0)";resolution:=optional
    (...)

2. EXPORTING PACKAGES

    示例：

    Export-Package: org.springframework.orm;version="2.5.6.A",
    (...)

3. GIVING AN IDENTITY TO A BUNDLE

    Bundle-SymbolicName: org.springframework.core  //必须的，只能是字母，下划线，连字符
    Bundle-Version: 2.5.6.A   //必须的，和上一个Header一起唯一标示一个Bundle
    Bundle-Name: Spring Core   //可选的，方便开发人员阅读

4. JAR打包规范

    ■ The META-INF/MANIFEST.MF file must be the first entry in the JAR, and the jar command

       enforces this rule (so you shouldn’t try to package your OSGi bundles manually).
    ■ The manifest format has strict requirements. For instance, lines can’t be longer than 72

       characters and the file should end with an empty line.

    参考：http://download.oracle.com/javase/1.5.0/docs/guide/jar/jar.html

5. Bun Tool

    (1) 下载地址：http://www.aqute.biz/repo/biz/aQute/bnd/

    (2) Create OSGi Bundle: http://blog.springsource.com/2008/02/18/creating-osgi-bundles/

6. 案例演示：The Bud Tool

    以commons-logging-1.1.1.jar为例,bnd-0.0.401.jar重命名为bnd.jar方便使用，见附件。

    (1)检查一个JAR文件内部结构

    java -jar bnd.jar commons-logging-1.1.1.jar

    (2) 打开MAINFEST.MF文件及检查Package依赖   

    java -jar bnd.jar print commons-logging-1.1.1.jar

    (3) 生成OSGi格式的Bundle

    java -jar bnd.jar wrap commons-logging-1.1.1.jar

    将生成commons-logging-1.1.1.bar, 查看该Bar文件的MAINFEST.MF文件：

    java -jar bnd.jar print commons-logging-1.1.1.bar

    默认情况下，wrap命令使用的property文件为：

    Export-Package: *
    Import-Package: AllReferencedPackages

    若需明确指定需要Import或Export的Package,可参考(5).

    (4)指定新生成的Bundle

    java -jar bnd.jar wrap -output commons-logging-osgi-1.1.1.jar  commons-logging-1.1.1.jar

    将生成OSGi格式的Bundle:commons-logging-osgi-1.1.1.jar

    (5)精确指定生成的MAINFEST.MF中的内容：增加Properties文件

    commons-logging-1.1.1.bnd:
    # Assign version
    version=1.1.1
    # Assign name
    bundle_name=commons.logging
    Bundle-Name: OSGi'fied Common Logging- ${bundle_name} ${version}
    Bundle-SymbolicName: ${bundle_name}
    Bundle-Version: ${version}

    Export-Package: org.apache.commons.logging;version=${version}
    Private-Package: org.apache.commons.logging.impl

    命令：

    java -jar bnd.jar wrap -output commons-logging-osgi-1.1.1.jar -properties   commons-logging-1.1.1.bnd commons-logging-1.1.1.jar