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本文主要研究一下arthas的spring-boot-starter

ArthasConfiguration

arthas-spring-boot-starter/src/main/java/com/alibaba/arthas/spring/ArthasConfiguration.java

@ConditionalOnProperty(name = "spring.arthas.enabled", matchIfMissing = true)
@EnableConfigurationProperties({ ArthasProperties.class })
public class ArthasConfiguration {
    private static final Logger logger = LoggerFactory.getLogger(ArthasConfiguration.class);

    @Autowired
    ConfigurableEnvironment environment;

    /**
     * <pre>
     * 1. 提取所有以 arthas.* 开头的配置项，再统一转换为Arthas配置
     * 2. 避免某些配置在新版本里支持，但在ArthasProperties里没有配置的情况。
     * </pre>
     */
    @ConfigurationProperties(prefix = "arthas")
    @ConditionalOnMissingBean(name="arthasConfigMap")
    @Bean
    public HashMap<String, String> arthasConfigMap() {
        return new HashMap<String, String>();
    }

    @ConditionalOnMissingBean
    @Bean
    public ArthasAgent arthasAgent(@Autowired @Qualifier("arthasConfigMap") Map<String, String> arthasConfigMap,
            @Autowired ArthasProperties arthasProperties) throws Throwable {
        arthasConfigMap = StringUtils.removeDashKey(arthasConfigMap);
        ArthasProperties.updateArthasConfigMapDefaultValue(arthasConfigMap);
        /**
         * @see org.springframework.boot.context.ContextIdApplicationContextInitializer#getApplicationId(ConfigurableEnvironment)
         */
        String appName = environment.getProperty("spring.application.name");
        if (arthasConfigMap.get("appName") == null && appName != null) {
            arthasConfigMap.put("appName", appName);
        }

        // 给配置全加上前缀
        Map<String, String> mapWithPrefix = new HashMap<String, String>(arthasConfigMap.size());
        for (Entry<String, String> entry : arthasConfigMap.entrySet()) {
            mapWithPrefix.put("arthas." + entry.getKey(), entry.getValue());
        }

        final ArthasAgent arthasAgent = new ArthasAgent(mapWithPrefix, arthasProperties.getHome(),
                arthasProperties.isSlientInit(), null);

        arthasAgent.init();
        logger.info("Arthas agent start success.");
        return arthasAgent;

    }
}

ArthasConfiguration注册了arthasConfigMap及arthasAgent两个bean

ArthasAgent

arthas-agent-attach/src/main/java/com/taobao/arthas/agent/attach/ArthasAgent.java

public class ArthasAgent {
    private static final int TEMP_DIR_ATTEMPTS = 10000;

    private static final String ARTHAS_CORE_JAR = "arthas-core.jar";
    private static final String ARTHAS_BOOTSTRAP = "com.taobao.arthas.core.server.ArthasBootstrap";
    private static final String GET_INSTANCE = "getInstance";
    private static final String IS_BIND = "isBind";

    private String errorMessage;

    private Map<String, String> configMap = new HashMap<String, String>();
    private String arthasHome;
    private boolean slientInit;
    private Instrumentation instrumentation;

    public ArthasAgent() {
        this(null, null, false, null);
    }

    //......

    public void init() throws IllegalStateException {
        // 尝试判断arthas是否已在运行，如果是的话，直接就退出
        try {
            Class.forName("java.arthas.SpyAPI"); // 加载不到会抛异常
            if (SpyAPI.isInited()) {
                return;
            }
        } catch (Throwable e) {
            // ignore
        }

        try {
            if (instrumentation == null) {
                instrumentation = ByteBuddyAgent.install();
            }

            // 检查 arthasHome
            if (arthasHome == null || arthasHome.trim().isEmpty()) {
                // 解压出 arthasHome
                URL coreJarUrl = this.getClass().getClassLoader().getResource("arthas-bin.zip");
                if (coreJarUrl != null) {
                    File tempArthasDir = createTempDir();
                    ZipUtil.unpack(coreJarUrl.openStream(), tempArthasDir);
                    arthasHome = tempArthasDir.getAbsolutePath();
                } else {
                    throw new IllegalArgumentException("can not getResources arthas-bin.zip from classloader: "
                            + this.getClass().getClassLoader());
                }
            }

            // find arthas-core.jar
            File arthasCoreJarFile = new File(arthasHome, ARTHAS_CORE_JAR);
            if (!arthasCoreJarFile.exists()) {
                throw new IllegalStateException("can not find arthas-core.jar under arthasHome: " + arthasHome);
            }
            AttachArthasClassloader arthasClassLoader = new AttachArthasClassloader(
                    new URL[] { arthasCoreJarFile.toURI().toURL() });

            /**
             * <pre>
             * ArthasBootstrap bootstrap = ArthasBootstrap.getInstance(inst);
             * </pre>
             */
            Class<?> bootstrapClass = arthasClassLoader.loadClass(ARTHAS_BOOTSTRAP);
            Object bootstrap = bootstrapClass.getMethod(GET_INSTANCE, Instrumentation.class, Map.class).invoke(null,
                    instrumentation, configMap);
            boolean isBind = (Boolean) bootstrapClass.getMethod(IS_BIND).invoke(bootstrap);
            if (!isBind) {
                String errorMsg = "Arthas server port binding failed! Please check $HOME/logs/arthas/arthas.log for more details.";
                throw new RuntimeException(errorMsg);
            }
        } catch (Throwable e) {
            errorMessage = e.getMessage();
            if (!slientInit) {
                throw new IllegalStateException(e);
            }
        }
    }
}    

ArthasAgent的init方法先尝试加载java.arthas.SpyAPI，若SpyAPI.isInited()为true则直接返回；之后执行ByteBuddyAgent.install()；对于arthasHome为null则尝试读取arthas-bin.zip文件，接着创建AttachArthasClassloader，加载com.taobao.arthas.core.server.ArthasBootstrap，执行其getInstance方法，再对实例执行isBind

ArthasEndPointAutoConfiguration

arthas-spring-boot-starter/src/main/java/com/alibaba/arthas/spring/endpoints/ArthasEndPointAutoConfiguration.java

@ConditionalOnProperty(name = "spring.arthas.enabled", matchIfMissing = true)
public class ArthasEndPointAutoConfiguration {

    @Bean
    @ConditionalOnMissingBean
    @ConditionalOnAvailableEndpoint
    public ArthasEndPoint arthasEndPoint() {
        return new ArthasEndPoint();
    }
}

ArthasEndPointAutoConfiguration则创建ArthasEndPoint

ArthasEndPoint

arthas-spring-boot-starter/src/main/java/com/alibaba/arthas/spring/endpoints/ArthasEndPoint.java

@Endpoint(id = "arthas")
public class ArthasEndPoint {

    @Autowired(required = false)
    private ArthasAgent arthasAgent;

    @Autowired(required = false)
    private HashMap<String, String> arthasConfigMap;

    @ReadOperation
    public Map<String, Object> invoke() {
        Map<String, Object> result = new HashMap<String, Object>();

        if (arthasConfigMap != null) {
            result.put("arthasConfigMap", arthasConfigMap);
        }

        String errorMessage = arthasAgent.getErrorMessage();
        if (errorMessage != null) {
            result.put("errorMessage", errorMessage);
        }

        return result;
    }

}

ArthasEndPoint提供了一个读方法返回arthasConfigMap

小结

arthas的spring-boot-starter有两个自动配置，分别是ArthasConfiguration及ArthasEndPointAutoConfiguration，其中ArthasConfiguration注册了arthasConfigMap及arthasAgent两个bean，而ArthasEndPointAutoConfiguration则创建ArthasEndPoint。