API Mediation Layer Message Service Component

The API ML Message Service component unifies and stores REST API error messages and log messages in a single file. The Message Service component enables users to mitigate the problem of message definition redundancy which helps to optimize the development process.

• Message Definition
• Creating a message
• Mapping a message
• API ML Logger

Message Definition

API ML uses a customizable infrastructure to format both REST API error messages and log messages. yaml files make it possible to centralize both API error messages and log messages. Messages have the following definitions:

• Message key - a unique ID in the form of a dot-delimited string that describes the reason for the message. The key enables the UI or the console to show a meaningful and localized message.

  Tips:

  • We recommend using the format org.zowe.sample.apiservice.{TYPE}.greeting.empty to define the message key. {TYPE} can be the api or log keyword.

  • Use the message key and not the message number. The message number makes the code less readable, and increases the possibility of errors when renumbering values inside the number.

• Message number - a typical mainframe message ID (excluding the severity code)

• Message type - There are two Massage types:

  • REST API error messages: ERROR
  • Log messages: ERROR, WARNING, INFO, DEBUG, or TRACE

• Message text - a description of the issue

The following example shows the message definition.

Example:

messages:
    - key: org.zowe.sample.apiservice.{TYPE}.greeting.empty
      number: ZWEASA001
      type: ERROR
      text: "The provided '%s' name is empty."

Creating a message

Use the following classes when you create a message:

• org.zowe.apiml.message.core.MessageService - lets you create a message from a file.
• org.zowe.apiml.message.yaml.YamlMessageService - implements org.zowe.apiml.message.core.MessageService so that org.zowe.apiml.message.yaml.YamlMessageService can read message information from a yaml file, and create a message with message parameters.

Use the following process to create a message.

Follow these steps:

1. Load messages from the yaml file.

   Example:

   MessageService messageService = new YamlMessageService();
   messageService.loadMessages("/api-messages.yml");
   messageService.loadMessages("/log-messages.yml");

2. Use the Message createMessage(String key, Object... parameters); method to create a message.

   Example:

   Message message = messageService.createMessage("org.zowe.sample.apiservice.{TYPE}.greeting.empty", "test");

Mapping a message

You can map the Message either to a REST API response or to a log message.

When you map a REST API response, use the following methods:

• mapToView - returns a UI model as a list of API Message, and can be used for Rest API error messages
• mapToApiMessage - returns a UI model as a single API Message

The following example is a result of using the mapToView method.

Example:

{
"messages": [
  {
    "messageKey": "org.zowe.sample.apiservice.{TYPE}.greeting.empty",
    "messageType": "ERROR",
    "messageNumber": "ZWEASA001",
    "messageContent": "The provided 'test' name is empty."
  }
  ]
}

The following example is the result of using the mapToApiMessage method.

Example:

{
  "messageKey": "org.zowe.sample.apiservice.{TYPE}.greeting.empty",
  "messageType": "ERROR",
  "messageNumber": "ZWEASA001",
  "messageContent": "The provided 'test' name is empty."
}

API ML Logger

The org.zowe.apiml.message.log.ApimLogger component controls messages through the Message Service component.

The following example uses the log message definition in a yaml file.

Example:

messages:
    - key: org.zowe.sample.apiservice.log.greeting.empty
      number: ZWEASA001
      type: DEBUG
      text: "The provided '%s' name is empty."

When you map a log message, use mapToLogMessage to return a log message as text. The following example is the output of the mapToLogMessage.

Example:

ZWEASA001D The provided ‘test’ name is empty. {43abb594-3415-4ed5-a0b5-23e306a91124}

Use the ApimlLogger to log messages which are defined in the yaml file.

Example:

package org.zowe.apiml.client.configuration;

import org.zowe.apiml.message.core.MessageService;
import org.zowe.apiml.message.core.MessageType;
import org.zowe.apiml.message.log.ApimlLogger;

public class SampleClass {

   private final ApimlLogger logger;

   public SampleClass(MessageService messageService) {
       logger = ApimlLogger.of(SampleClass.class, messageService);
   }

   public void process() {
       logger.log(“org.zowe.sample.apiservice.log.greeting.empty”, “test”);

   }

}

The following example shows the output of a successful ApimlLogger usage.

Example:

DEBUG (c.c.m.c.c.SampleClass) ZWEASA001D The provided 'test' name  is empty. {43abb594-3415-4ed5-a0b5-23e306a91124}