Java SDK實現了“上下文”的概念，以支援將附加資訊附加到事件，例如麵包屑。上下文可以指向Web框架的單個請求，Android應用程式的整個生命週期，或者更適合您的應用程式需求的其他內容。 沒有單一的上下文定義適用於每個應用程式，因此必須根據應用程式的功能和結構來選擇特定的實現。預設情況下，Sentry使用ThreadLocalContextManager，每個執行緒維護一個Context例項。這對於每個使用者請求使用一個執行緒的框架（例如基於同步servlet API的框架）非常有用。 Sentry還安裝了一個ServletRequestListener，它將在每個servlet請求完成後清除執行緒的上下文。 Sentry預設使用Android上的SingletonContextManager，它在應用程式的生命週期內為所有執行緒維護單個上下文例項。 要覆蓋ContextManager，您需要覆蓋DefaultSentryClientFactory中的getContextManager方法。將來可能會提供更簡單的API。

一、使用用法

麵包屑可用於描述導致傳送事件的應用程式中發生的操作。例如，是否發出了外部API請求，或者使用者是否單擊了Android應用程式中的某些內容。預設情況下，每個上下文的最後100個麵包屑將被儲存並與未來事件一起傳送。 可以根據上下文設定使用者，以便了解每個事件的影響。 初始化SentryClient例項後，您可以開始在當前上下文中設定狀態。

import io.sentry.Sentry;
import io.sentry.context.Context;
import io.sentry.event.BreadcrumbBuilder;
import io.sentry.event.UserBuilder;

public class MyClass {

    /**
      * Examples using the (recommended) static API.
      */
    public void staticAPIExample() {
        // Manually initialize the static client, you may also pass in a DSN and/or
        // SentryClientFactory to use. Note that the client will attempt to automatically
        // initialize on the first use of the static API, so this isn't strictly necessary.
        Sentry.init();

        // Note that all fields set on the context are optional. Context data is copied onto
        // all future events in the current context (until the context is cleared).

        // Set the current user in the context.
        Sentry.getContext().setUser(
            new UserBuilder().setUsername("user1").build()
        );

        // Record a breadcrumb in the context.
        Sentry.getContext().recordBreadcrumb(
            new BreadcrumbBuilder().setMessage("User did something specific again!").build()
        );

        // Add extra data to future events in this context.
        Sentry.getContext().addExtra("extra", "thing");

        // Add an additional tag to future events in this context.
        Sentry.getContext().addTag("tagName", "tagValue");

        // Send an event with the context data attached.
        Sentry.capture("New event message");

        // Clear the context, useful if you need to add hooks in a framework
        // to empty context between requests.
        Sentry.clearContext();
    }

    /**
      * Examples that use the SentryClient instance directly.
      */
    public void instanceAPIExample() {
        // Create a SentryClient instance that you manage manually.
        SentryClient sentryClient = SentryClientFactory.sentryClient();

        // Get the current context instance.
        Context context = sentryClient.getContext();

        // Note that all fields set on the context are optional. Context data is copied onto
        // all future events in the current context (until the context is cleared).

        // Set the current user in the context.
        context.setUser(
            new UserBuilder().setUsername("user1").build()
        );

        // Record a breadcrumb in the context.
        context.recordBreadcrumb(
            new BreadcrumbBuilder().setMessage("User did something specific!").build()
        );

        // Add extra data to future events in this context.
        context.addExtra("extra", "thing");

        // Add an additional tag to future events in this context.
        context.addTag("tagName", "tagValue");

        // Send an event with the context data attached.
        sentryClient.sendMessage("New event message");

        // Clear the context, useful if you need to add hooks in a framework
        // to empty context between requests.
        context.clear();
    }
}