This page describes the WSO2 ESB architecture in the following sections:
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Proxy services are virtual services that receive messages and optionally process them before forwarding them to a service at a given endpoint. This approach allows you to perform necessary transformations and introduce additional functionality without changing your existing service. Any available transport can be used to receive and send messages from the proxy services. A proxy service is externally visible and can be accessed using a URL similar to a normal web service address.
See Working with Proxy Services.
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An API in WSO2 ESB is analogous to a web application deployed in the ESB runtime. Each API is anchored at a user-defined URL context, much like how a web application deployed in a servlet container is anchored at a fixed URL context. An API will only process requests that fall under its URL context. The API defines one or more resources, which is a logical component of an API that can be accessed by making a particular type of HTTP call. This approach allows you to send messages directly into the ESB using REST.
See Creating APIs.
Inbound endpoints
An inbound endpoint is a message source that can be configured dynamically. In the ESB, when it comes to the existing axis2 based transports, only the HTTP transport works in a multi-tenant mode. Inbound endpoints support all transports to work in a multi-tenant mode.
See Working with Inbound Endpoints
Topics
A topic allows services to receive messages when a specific type of event occurs by subscribing to messages that have been published to a specific topic.
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