tREST

Serves as a REST Web service client.

The tREST component sends HTTP
requests to a REpresentational State Transfer (REST) Web service
provider and gets responses correspondingly.

tREST Standard properties

These properties are used to configure tREST running in the Standard Job framework.

The Standard
tREST component belongs to the Internet family.

The component in this framework is generally available.

Basic settings

Warning:

To build Jobs that need to be deployed into the Talend Runtime,
it is recommended to use the tRESTClient component which
is best suited for the Talend Runtime.

For more information about the
tRESTClient component, see tRESTClient.

Schema and Edit Schema	A schema is a row description, it defines the number of fields that will be processed and passed on to the next component. This component always uses a built-in, read-only schema that contains two columns: – Body: stores the result from the server end. – ERROR_CODE: stores the HTTP status code from the server end when an error occurs during the invocation process. The specific meanings of the errors codes are subject to definitions of your Web service provider. For reference information, visit en.wikipedia.org/wiki/List_of_HTTP_status_codes. Click Edit Schema to view the schema structure. Warning: Changing the schema type may result in loss of the schema structure and therefore failure of the component.
URL	Type in the URL address of the REST Web server to be invoked.
HTTP Method	From this list, select an HTTP method that describes the desired action. The specific meanings of the HTTP methods are subject to definitions of your Web service provider. Listed below are the generally accepted HTTP method definitions: – GET: retrieves data from the server end based on the given parameters. – POST: creates and uploads data based on the given parameters. – PUT: updates data based on the given parameters, or if the data does not exist, creates it. – DELETE: removes data based on the given parameters.
HTTP Headers	Type in the name-value pair(s) for HTTP headers to define the parameters of the requested HTTP operation. For the specific definitions of HTTP headers, consult your REST Web service provider. For reference information, visit en.wikipedia.org/wiki/List_of_HTTP_headers.
HTTP Body	Type in the payload to be uploaded to the server end when the POST or PUT action is selected.

Advanced settings

tStatCatcher Statistics	Select this check box to gather the Job processing metadata at the Job level as well as at each component level.

Global Variables

Global Variables	ERROR_MESSAGE: the error message generated by the component when an error occurs. This is an After variable and it returns a string. This variable functions only if the Die on error check box is cleared, if the component has this check box. A Flow variable functions during the execution of a component while an After variable functions after the execution of the component. To fill up a field or expression with a variable, press Ctrl + Space to access the variable list and choose the variable to use from it. For further information about variables, see Talend Studio User Guide.

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space to access the variable list and choose the variable to use from it.

For further information about variables, see
Talend Studio

User Guide.

Usage

Usage rule	Use this component as a REST Web service client to communicate with a REST Web service provider. It must be linked to an output component.
Limitation	JRE 1.6 must be running for this component to work properly.

Scenario: Creating and retrieving data by invoking REST Web service

This scenario describes a simple Job that invokes a REST Web service to create a new
customer record on the server end and then retrieve the customer information. When
executed, the Job displays relevant information on the Run console.

Drop the following components from the Palette onto the design workspace: two tREST components and two tLogRow components, and label the two tREST components to best describe the actions to perform.
Connect each tREST to one tLogRow using a Row
> Main connection.
Connect the first tREST to the second
tREST using a Trigger > OnSubjobOK
connection.

Double click the first tREST component to
open its Basic settings view.

Fill the URL field with the URL of the Web
service you are going to invoke. Note that the URL provided in this use case is
for demonstration purposes only and is not a live address.
From the HTTP Method list, select POST to send an HTTP request for creating a new
record.
Click the plus button to add a line in the HTTP
Headers table, and type in the appropriate name-value key pair,
which is subject to definition of your service provider, to indicate the media
type of the payload to send to the server end. In this use case, type in
Content-Type and application/xml.
For reference information about Internet media types, visit www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.7.
Fill the HTTP Body field with the payload to
be uploaded to the server end. In this use case, type in
<Customer><name>Steven</name></Customer>
to create a record for a new customer named Steven.

Note:

If you want to include double quotation marks in your payload, be sure to use a
backslash escape character before each of the quotation marks. In this use case, for
example, type in
<Customer><name>”Steven”</name></Customer>
if you want to enclose the name Steven in a pair of double
quotation marks.

Double click the second tREST component to
open its Basic settings view.
Fill the URL field with the same URL.
From the HTTP Method list, select GET to send an HTTP request for retrieving the
existing records.
In the Basic settings view of each tLogRow, select the Print
component unique name in front of each output row and Print schema column name in front of each value check
boxes for better identification of the output flows.

Save your Job and press F6 to launch it.

The console shows that the first tREST
component sends an HTTP request to the server end to create a new customer named
Steven, and the second tREST component successfully reads data from the server end,
which includes the information of the new customer you just created.

Document get from Talend https://help.talend.com

Thank you for watching.

Docs 6.x

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tREST – Docs for ESB 6.x