Introduction to WSO2 ESB
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This document discusses key concepts in WSO2 Enterprise Service Bus including mediators, sequences, endpoints, proxy services, and API management. It describes how mediators can transform and route messages through a sequence. Endpoints define references to services and set constraints. Proxy services receive and route client requests to backend services. APIs expose resources through HTTP and can be restricted with URI templates.
Introduction to WSO2 ESB
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- 26. • The simplest functional component available in WSO2 ESB • A black box which accepts a message and carries out a predefined task on it • WSO2 ESB comes with a rich library of built-in mediators –Log mediator : Logs the message –Send mediator: Sends the message to a URL –XSLT mediator : Performs an XSLT transformation on the message Configuration Data Input Message Output Message
- 27. … • Transforming messages –eg: XSLT mediator, Payload factory mediator • Manipulating message headers and properties –eg: Header mediator, Property mediator • Replicating, splitting and aggregating messages –eg: Clone mediator, Aggregate mediator • Filtering messages –eg: Filter mediator, Switch mediator • Custom Mediation –Eg: Class mediator, Script mediator • And lot more… –http://docs.wso2.org/display/ESB481/Mediators - complete list
- 28. • A sequential arrangement of mediators – A mediator chain! • When a message is handed to a sequence it is given to the first mediator of the chain - The outcome of that will be handed to the second mediator of the chain and so on… • The messages are sent through the chain while mediators perform various actions on it along the way • Pipelining in action!
- 29. … ● Consider the example sequence shown above − Messages are first logged by the log mediator − The property mediator sets a property on the messages − Then they are sent to a specified endpoint by the send mediator − It is a simple log-and-forward message flow!
- 30. ● Defines an endpoint reference (EPR) to which messages can be sent/forwarded from the ESB − The send mediator takes an endpoint as an argument ● Various operational constraints can be enforced on an endpoint − Timeout duration − Message format (REST, POX, SOAP 1.1, SOAP 1.2) ● QoS expectations can be set on an endpoint − Security
- 31. ● Main types of endpoints − Address endpoint (A simple URL) − WSDL endpoint (Extracts the EPR from a WSDL) − HTTP endpoint ( To invoke REST services with URL parameters) − Default endpoint ( Adding QoS and other constraints) − Load balance endpoints (Divides the requests among several child endpoints) − Fail over endpoints (Detects errors that can occur while sending the messages and resends them to a backup endpoint)
- 32. ● Acts like a virtual service that can receive requests from clients ● Received client requests are processed and routed to a specified endpoint (usually to an actual service – backend service) ● Responses coming back from the backend service are further processed and forwarded to the clients ● Resembles traditional HTTP proxy servers
- 35. o If you have a REST front-end client, REST back-end service, or both a REST client and service, you can use a proxy service in the ESB to handle the communication between the front end and back end o REST Client and SOAP Service o SOAP Client and REST Service o REST Client and REST Service o JMS Client and REST Service o https://docs.wso2.org/display/ESB481/Using+REST+with+a+Proxy+Service *
- 36. o API anchored at URL context o e.g., GET /test o Resources o Component of API accessed through HTTP call o Similar to proxy service (in, out, and fault sequences) but more limited o Can restrict resource’s scope using URL patterns and URI templates *
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- 38. o URL mapping oPath mappings (eg: /test/*, /foo/bar/*) oExtension mappings (eg: *.jsp, *.do) oExact mappings (eg: /test, /test/foo) o URI template o/order/{orderId} would process /order/A0001 o/dictionary/{char}/{word} would process /dictionary/c/cat o Use get-property to retrieve exact values <log level="custom"> <property name="Character" expression="get- property('uri.var.char')"/> <property name="Word" expression="get-property ('uri.var.word')"/> </log> *
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