OSGi的简单代码示例

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Tags: osgi felix

OSGi(Open Service Gateway Initiative)是面向Java的动态模型系统，使用OSGi可以进行模块的动态加载，无需停止重启服务器，而模块就是我们下面要开发的Bundle。OSGi在电信或其他大型企业里面用的比较多，Eclipse现在也是用osgi的方式来添加插件。

IntelliJ IDEA的OSGi环境搭建

  • 我们使用Felix这个OSGi框架来进行OSGi代码的开发，首先我们下载最新版本的Felix包并解压
  • 在IDEA进行OSGi的设置，选择刚才解压好的felix目录
  • 写一个简单的Activator，下面要用到
HelloActivator.java
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package com.zzm.osgi;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

public class HelloActivator implements BundleActivator {
    public void start(BundleContext bundleContext) throws Exception {
        System.out.println("Hello World Bundle started!");
    }

    public void stop(BundleContext bundleContext) throws Exception {
        System.out.println("Hello World Bundle stop!");
    }
}
  • 在工程设置页面进行设置，写上bundle对应的Activator
  • 在Run菜单中添加osgi的运行配置，Run->Edit Configurations…
  • 运行felix

可以看到IDEA已经帮我们自动启动了我们的Activator，打印了Hello World Start的语句。

输入lb查看所有bundle的信息，可以看到最下面是我们的bundle，已经激活。

我们停掉bundle，再显示所有bundle状态，可以看到我们的bundle的状态已经是Resolved了。

使用felix的Maven Bundle插件来创建bundle

上面是通过IDE来启动和创建bundle，我们再来看下使用felix maven插件的方式创建bundle，这里是官网地址说明: http://felix.apache.org/site/apache-felix-maven-bundle-plugin-bnd.html。

  • 首先新建Maven的pom.xml文件
    • 在dependencies加入felix的jar包，最新的版本是1.4.0
    • 在plugin中定义我们的bundle，包括我们的Activator等信息。
    • packaging需要修改为bundle
pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.zzm</groupId>
    <artifactId>osgi</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>bundle</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-bundle-plugin</artifactId>
                <version>2.4.0</version>
                <extensions>true</extensions>

                <configuration>
                    <instructions>
                        <Bundle-SymbolicName>${pom.groupId}.${pom.artifactId}</Bundle-SymbolicName>
                        <Bundle-Vendor>Apache Felix</Bundle-Vendor>
                        <Bundle-Activator>com.zzm.osgi.HelloActivator</Bundle-Activator>
                        <Private-Package>com.zzm.osgi</Private-Package>
                    </instructions>
                </configuration>
            </plugin>

        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.osgi.core</artifactId>
            <version>1.4.0</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

</project>
  • 还是使用我们之前的Activator，在工程根目录下使用maven进行打包，打包完后可以在target目录下面看到打好的bundle包。
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$ mvn clean install
...balabala

[INFO] 
[INFO] --- maven-bundle-plugin:2.4.0:bundle (default-bundle) @ osgi ---
[INFO] 
[INFO] --- maven-install-plugin:2.5.2:install (default-install) @ osgi ---
[INFO] Installing /Users/zhaozhiming/projects/hello_osgi/bundles/osgi-1.0-SNAPSHOT.jar to /Users/zhaozhiming/.m2/repository/com/zzm/osgi/1.0-SNAPSHOT/osgi-1.0-SNAPSHOT.jar
[INFO] Installing /Users/zhaozhiming/projects/hello_osgi/pom.xml to /Users/zhaozhiming/.m2/repository/com/zzm/osgi/1.0-SNAPSHOT/osgi-1.0-SNAPSHOT.pom
[INFO] 
[INFO] --- maven-bundle-plugin:2.4.0:install (default-install) @ osgi ---
[INFO] Installing com/zzm/osgi/1.0-SNAPSHOT/osgi-1.0-SNAPSHOT.jar
[INFO] Writing OBR metadata
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.898s
[INFO] Finished at: Sat Jan 31 10:44:49 HKT 2015
[INFO] Final Memory: 18M/216M
[INFO] ------------------------------------------------------------------------

$ cd target
$ ls -l
total 8
drwxr-xr-x  4 zhaozhiming  staff   136 Jan 31 10:57 classes
drwxr-xr-x  3 zhaozhiming  staff   102 Jan 31 10:57 maven-status
-rw-r--r--  1 zhaozhiming  staff  2901 Jan 31 10:57 osgi-1.0-SNAPSHOT.jar
drwxr-xr-x  4 zhaozhiming  staff   136 Jan 31 10:57 surefire-reports
drwxr-xr-x  3 zhaozhiming  staff   102 Jan 31 10:57 test-classes

  • 打完包后，在target/classes/META-INF目录下，可以看到maven会产生一个MANIFEST.MF文件，显示了bundle的具体信息。
MANIFEST.MF
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Manifest-Version: 1.0
Bnd-LastModified: 1422673028905
Build-Jdk: 1.8.0_25
Built-By: zhaozhiming
Bundle-Activator: com.zzm.osgi.HelloActivator
Bundle-ManifestVersion: 2
Bundle-Name: osgi
Bundle-SymbolicName: com.zzm.osgi
Bundle-Vendor: Apache Felix
Bundle-Version: 1.0.0.SNAPSHOT
Created-By: Apache Maven Bundle Plugin
Export-Package: com.zzm.osgi;uses:="org.osgi.framework";version="1.0.0.S
 NAPSHOT"
Import-Package: org.osgi.framework;version="[1.5,2)"
Tool: Bnd-2.1.0.20130426-122213
  • 在felix中运行bundle
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# 拷贝bundle包
$ cp osgi-1.0-SNAPSHOT.jar /your/felix/parent/folder
$ cd /your/felix/parent/folder
$ ls
drwxr-xr-x@ 12 zhaozhiming  staff   408 Jan 30 13:39 felix
-rw-r--r--   1 zhaozhiming  staff  2901 Jan 31 11:18 osgi-1.0-SNAPSHOT.jar

# 启动felix
$ cd felix
$ java -jar bin/felix.jar
____________________________
Welcome to Apache Felix Gogo

g! 

# 查看所有bundle
g! lb
START LEVEL 1
   ID|State      |Level|Name
    0|Active     |    0|System Bundle (4.6.0)
    1|Active     |    1|Apache Felix Bundle Repository (2.0.2)
    2|Active     |    1|Apache Felix Gogo Command (0.14.0)
    3|Active     |    1|Apache Felix Gogo Runtime (0.12.1)
    4|Active     |    1|Apache Felix Gogo Shell (0.10.0)
    5|Active     |    1|Sample01 (1.0.0.SNAPSHOT)

# 安装我们的bundle
g! install file:../osgi-1.0-SNAPSHOT.jar
Bundle ID: 253

# 查看bundle信息
g! lb
START LEVEL 1
   ID|State      |Level|Name
   ...
  253|Installed  |    1|osgi (1.0.0.SNAPSHOT)
  
# 启动我们的bundle
g! start 253
Hello World Bundle start!
g! lb  
START LEVEL 1
   ID|State      |Level|Name
    ...
  253|Active     |    1|osgi (1.0.0.SNAPSHOT)

# 停掉我们的bundle
g! stop 253
Hello World Bundle stop!
g! lb
START LEVEL 1
   ID|State      |Level|Name
   ...
  253|Resolved   |    1|osgi (1.0.0.SNAPSHOT)

# 卸载我们的bundle，可以看到已经没有出现在所有bundle信息中了
g! uninstall 253
g! lb
START LEVEL 1
   ID|State      |Level|Name
    0|Active     |    0|System Bundle (4.6.0)
    1|Active     |    1|Apache Felix Bundle Repository (2.0.2)
    2|Active     |    1|Apache Felix Gogo Command (0.14.0)
    3|Active     |    1|Apache Felix Gogo Runtime (0.12.1)
    4|Active     |    1|Apache Felix Gogo Shell (0.10.0)
    5|Active     |    1|Sample01 (1.0.0.SNAPSHOT)

# 最后`ctl+c`退出felix

在bundle中添加第三方包

在bundle中使用第三方包比较麻烦，查看了各方资料，只找到了把第三方jar包一起打进bundle的方法，我们以引入guava包为例，下面代码加注释的就是修改的地方。

pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.zzm</groupId>
    <artifactId>osgi</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>bundle</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.felix</groupId>
                <artifactId>maven-bundle-plugin</artifactId>
                <version>2.4.0</version>
                <extensions>true</extensions>

                <configuration>
                <!--修改bundle配置  -->
                    <instructions>
                        <Bundle-SymbolicName>${pom.groupId}.${pom.artifactId}</Bundle-SymbolicName>
                        <Bundle-Vendor>Apache Felix</Bundle-Vendor>
                        <Bundle-Activator>com.zzm.osgi.HelloActivator</Bundle-Activator>
                        <Private-Package>com.zzm.osgi</Private-Package>

                        <Embed-Dependency>
                            *;scope=compile|runtime;inline=false
                        </Embed-Dependency>
                        <_exportcontents>*</_exportcontents>
                        <Bundle-ClassPath>.,{maven-dependencies}</Bundle-ClassPath>
                        <Embed-Transitive>true</Embed-Transitive>
                        <Embed-Directory>jars</Embed-Directory>
                        <Embed-StripGroup>true</Embed-StripGroup>
                        <_failok>true</_failok>
                        <_nouses>true</_nouses>
                    </instructions>
                </configuration>
            </plugin>

            <!-- 添加依赖包copy插件 -->
            <plugin>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <id>copy-dependencies</id>
                        <phase>package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>jars</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>org.apache.felix</groupId>
            <artifactId>org.osgi.core</artifactId>
            <version>1.4.0</version>
            <scope>provided</scope>
        </dependency>

        <!-- 在pom中添加guava依赖 -->
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>18.0</version>
        </dependency>
    </dependencies>
</project>
  • 在Activator中添加guava的代码
HelloActivator.java
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public class HelloActivator implements BundleActivator {
    public void start(BundleContext bundleContext) throws Exception {
        System.out.println("Hello World Bundle start!");
        List<String> strings = Lists.newArrayList("I", "use", "guava", "here");
        System.out.println(strings);
    }
    ...
}
  • 打包运行我们的bundle
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$ mvn clean install 
$ cp osgi-1.0-SNAPSHOT.jar /your/felix/parent/folder
$ cd /your/felix/parent/folder
$ java -jar bin/felix.jar
____________________________
Welcome to Apache Felix Gogo

g! install file:../osgi-1.0-SNAPSHOT.jar
Bundle ID: 258
g! start 258
Hello World Bundle start!
[I, use, guava, here]
  • 可以解压我们的bundle jar包看一下结构
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$ mkdir jar_tar
$ cp osgi-1.0-SNAPSHOT.jar jar_tar/
$ cd jar_tar/
$ tar -xvf osgi-1.0-SNAPSHOT.jar
$ ls -l # 可以看到有个jars的文件夹
drwxr-xr-x  4 zhaozhiming  staff      136 Jan 31 11:56 META-INF
drwxr-xr-x  3 zhaozhiming  staff      102 Jan 31 11:44 com
drwxr-xr-x  3 zhaozhiming  staff      102 Jan 31 11:44 jars
-rw-r--r--  1 zhaozhiming  staff  1998876 Jan 31 11:55 osgi-1.0-SNAPSHOT.jar
$ ls -l jars # jars里面是我们的第三方包
-rwxr-xr-x  1 zhaozhiming  staff  2256213 Jan 30 10:07 guava-18.0.jar
  • 再看一下MANIFEST.MF文件，如下所示。
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Manifest-Version: 1.0
Bnd-LastModified: 1422675843327
Build-Jdk: 1.8.0_25
Built-By: zhaozhiming
Bundle-Activator: com.zzm.osgi.HelloActivator
Bundle-ClassPath: .,jars/guava-18.0.jar
Bundle-ManifestVersion: 2
Bundle-Name: osgi
Bundle-SymbolicName: com.zzm.osgi
Bundle-Vendor: Apache Felix
Bundle-Version: 1.0.0.SNAPSHOT
Created-By: Apache Maven Bundle Plugin
Embed-Dependency: *;scope=compile|runtime;inline=false
Embed-Directory: jars
Embed-StripGroup: true
Embed-Transitive: true
Embedded-Artifacts: jars/guava-18.0.jar;g="com.google.guava";a="guava";v
 ="18.0"
Export-Package: com.google.common.annotations;version="18.0.0",com.googl
 e.common.base;version="18.0.0",com.google.common.base.internal;version=
 "1.0.0.SNAPSHOT",com.google.common.cache;version="18.0.0",com.google.co
 mmon.collect;version="18.0.0",com.google.common.escape;version="18.0.0"
 ,com.google.common.eventbus;version="18.0.0",com.google.common.hash;ver
 sion="18.0.0",com.google.common.html;version="18.0.0",com.google.common
 .io;version="18.0.0",com.google.common.math;version="18.0.0",com.google
 .common.net;version="18.0.0",com.google.common.primitives;version="18.0
 .0",com.google.common.reflect;version="18.0.0",com.google.common.util.c
 oncurrent;version="18.0.0",com.google.common.xml;version="18.0.0",com.g
 oogle.thirdparty.publicsuffix;version="1.0.0.SNAPSHOT",com.zzm.osgi;ver
 sion="1.0.0.SNAPSHOT",jars;version="1.0.0.SNAPSHOT"
Import-Package: javax.annotation,org.osgi.framework;version="[1.5,2)",su
 n.misc
Tool: Bnd-2.1.0.20130426-122213

PS:在Import-Package中有sun.misc的字样，表示bundle引入了jdk的一些包，有时候在运行bundle的时候会看到下面的错误: 

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org.osgi.framework.BundleException: Unresolved constraint in bundle [8]: Unable to resolve 8.0: missing requirement [8.0] osgi.wiring.package; (osgi.wiring.package=sun.misc)

解决办法有2个，执行解决办法意味着你清楚并明确运行bundle时可以缺少这些包:

way1:是在pom文件中的中加入!sum.misc，这样打出来的MANIFEST.MF的Import-Package就不会有sun.misc字样了。

pom.xml
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<Bundle-SymbolicName>${project.groupId}.${project.artifactId}</Bundle-SymbolicName>
   <Bundle-Vendor>joyotime</Bundle-Vendor>
   <Bundle-Version>${project.version}</Bundle-Version>
   <Bundle-Activator>com.morewifi.chinatelecom.MoreWifiActivator</Bundle-Activator>
   <Private-Package>com.morewifi.chinatelecom</Private-Package>
   ...
   <Import-Package>
       !sun.misc,*
   </Import-Package>

way2:在felix解压包下有个conf/config.properties文件，在里面配置缺少的包。

felix/conf/config.properties
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org.osgi.framework.system.packages.extra=sun.misc

在bundle中保存文件

有时候在bundle中需要写一些数据到文件保存起来，可以使用bundleContext的getDataFile方法来获取文件，下面代码使用了guava的io方法。

HelloActivator.java
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public class HelloActivator implements BundleActivator {
    public void start(BundleContext bundleContext) throws Exception {
        System.out.println("Hello World Bundle start!");
        List<String> strings = Lists.newArrayList("I", "use", "guava", "here");
        System.out.println(strings);

        //保存文件
        File dataFile = bundleContext.getDataFile("save.txt");
        Files.append(strings.toString(), dataFile, Charsets.UTF_8);

        // 读取文件
        String fileContent = Files.readFirstLine(dataFile, Charsets.UTF_8);
        System.out.println(fileContent);
    }
    ...
}

打印结果如下: 

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g! start 263
Hello World Bundle start!
[I, use, guava, here]
[I, use, guava, here]

在felix的目录下，有个felix-cache目录，下面是各个bundle对应的文件夹，我们的save.txt就存放在bundle的data文件夹里面。

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$ cd felix-cache/bundle263/
$ ls -l 
-rw-r--r--  1 zhaozhiming  staff   54 Jan 31 13:51 bundle.info
drwxr-xr-x  3 zhaozhiming  staff  102 Jan 31 13:50 data
drwxr-xr-x  5 zhaozhiming  staff  170 Jan 31 13:50 version0.0
$ ls -l data
-rw-r--r--  1 zhaozhiming  staff  21 Jan 31 13:50 save.txt
$ cat data/save.txt 
[I, use, guava, here]

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