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Data Mapper mediator is a data mapping solution that can be integrated into a mediation sequence. It  It converts and transforms one data format to another, or changes the structure of the data in a message.   It provides a WSO2 Developer Studio-based tool to create a graphical mapping configuration and generates the files required to execute this graphical mapping configuration by the WSO2 Data Mapper engine.

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Prerequisites

You need to install the WSO2 Developer Studio ESB Tool 45.10.0 to use the Data Mapper mediator. For instructions on installing this WSO2 ESB Tooling Plugin, see Installing WSO2 ESB Tooling.

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WSO2 Data Mapper consists of two components. They are Data Mapper Tooling and Data Mapper Engine.

Data Mapper Tooling 

Data Mapper Tooling component is the interface used to create configuration files that are required by the Data Mapper Engine to execute the mapping. Following three configuration files are needed by the Data Mapper engine. 

• Input schema file
• Output schema file
• Mapping configuration file

These three files are generated by the Data Mapper Tool and saved in a Registry Resource project, which you deploy in a WSO2 server as shown in the example below.

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Input and output schema files

Input and output schema files are custom-defined JSON schemas that define the input/output format of input/output messages. The Data Mapper tool generates them when loading the input and output files as shown below.

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You can load the following input/output message formats:

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Mapping configuration file

This is a JavaScript file generated by looking at the diagram you draw in the Data Mapper Diagram Editor by connecting input elements to output elements. Every operation you define in the diagram gets converted to a JavaScript operation.

Data Mapper Engine

You need the following information to configure the Data Mapper Engine:

• Input message type
• Output message type
• Input schema Java Scripting API
• Output schema
• Mapping configuration

At the runtime, the Data Mapper Engine gets the input message and the runtime variable map object and outputs the transformed message. The Data Mapper Engine uses the Java Scripting API, t o execute the mapping configuration. Therefore, if your runtime is JAVA 7, it uses the Rhino JS Engine and if your runtime is JAVA 8, it uses the Nashorn JS engine.

When you use JAVA 7, there are several limitations in the Rhino engine that directly affects the Data mapper Engine. There are several functions that Rhino does not support. For example, String object functions like startsWith() and endsWith(). Therefore, the Rhino engine may have limitations in executing those when using custom functions and operators.

Using product-specific runtime variables

Also, the Data Mapper engine allows you to use runtime product-specific variables in the mapping. The intermediate component should construct a map object containing runtime product-specific variables and send it to the Data Mapper Engine, thereby, when the mapping happens in the Data Mapper Engine, these variables become available.

For example, the Data Mapper mediator provides ESB properties like  axis2/transport/synapse/axis2client/operation/.. In the Data Mapper diagram, you can use the  Property operator  and define the scope and the property name and use it in the mapping. Then, the Data Mapper mediator will identify the required properties to execute the mapping and populate a map with the required properties and will send it to the Data Mapper Engine. 

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Data Mapper element and attribute types

Following are the element and attribute types that are supported by the Data Mapper.

• {} - represents object elements
• [] - represents array elements
  
• <> - represents primitive field values
• A - represents XML attribute values

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Data Mapper operations

The operations palette placed in the left-hand side of the WSO2 Data Mapping Diagram Editor displays the operations that the Data Mapper supports as shown below.

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You can drag and drop these operations to the Editor area. There are six categories of operations as follows:

• Links
• Common
• Arithmetic
• Conditional
• Boolean
• Type Conversion
• String

Links

Image Modified   Data Mapping Link:  maps elements with other operators and elements.

Common

 Constant: defines String, number or boolean constant values.

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 Global Variable: instantiates global variables that you can access from anywhere. 

 Compare: compares two inputs in the mapping.

Arithmetic

 Add: adds two numbers.

 Subtract: subtracts two or more numbers.

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 Max: derives the maximum number from given inputs

Conditional

Image Modified   IfElse:  uses a condition and selects one input from given two.

Boolean 

 AND: performs the boolean AND operation on inputs. 

 OR: performs the boolean OR operation on inputs.

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{
  "books": {
    "book": {
      "id": "001",
      "author": "Writer",
      "title": "Great book on nature",
      "price": "44.95"
    }
  }
}

Samples

For a sample that demonstrates how to use the Data Mapper mediator, see:

• Using Data Mapper Mediator in WSO2 ESB