This is an example of a microservice application.

The aggregator application used for this microservice acts as a front-end for our application. It also aggregates and runs various algorithms to return the appropriate data.

The aggregator app has examples of:

• REST services
• REST client
• 3-tier architecture
• Basic POJO
• Service layer
• Controller layer
• (Spring) dependency injection
• HTTP request objects
• Logging API

The dictionary used for this microservice is from https://github.com/matthewreagan/WebstersEnglishDictionary

The dictionary app has examples of:

• REST services
• 3-tier architecture
• Basic POJO
• Static methods
• Static block
• Private methods
• Service layer
• Controller layer
• Data validation
• (Spring) dependency injection
• File I/O using the Java Stream API
• Mapping JSON to an object
• Logging API
• Usage of constants
• Logging performance metrics

The following are instructions on how to complete project 6 for a grade as well as what you can do for extra credit.

1. Add a method to the DictionaryService that returns all words that end with a certain value. To do this:

• Copy the getWordsStartingWith method
• Change the new method name to getWordsEndingWith
• Change the method call inside your new method from .startsWith to .endsWith

2. Add a method to the DictionaryController that calls your new service method and returns the words to the calling process. To do this:

• Copy the getWordsStartingWith method
• Change the new method name to getWordsEndingWith
• Change the method call to the service to getWordsEndingWith, which calls the method you created in step 1 above.
• Change the wording of the log message to reflect the new method's functionality.

3. Test your new endpoint using a browser or Postman

1. Add a method to the AggregatorRestClient that calls your new endpoint from above. To do this:

• Copy the getWordsStartingWith method
• Change the new method name to getWordsEndingWith
• Change the URI to the URI of your new dictionary endpoint

2. Add a method to the AggregatorService using the code below:

    public List<Entry> getAllPalindromes() {

        final List<Entry> candidates = new ArrayList<>();

        // Iterate from a to z
        IntStream.range('a', '{')
                 .mapToObj(i -> Character.toString(i))
                 .forEach(c -> {

                     // get words starting and ending with character
                     List<Entry> startsWith = restClient.getWordsStartingWith(c);
                     List<Entry> endsWith = restClient.getWordsEndingWith(c);

                     // keep entries that exist in both lists
                     List<Entry> startsAndEndsWith = new ArrayList<>(startsWith);
                     startsAndEndsWith.retainAll(endsWith);

                     // store list with existing entries
                     candidates.addAll(startsAndEndsWith);

                 });

        // test each entry for palindrome, sort and return
        return candidates.stream()
                         .filter(entry -> {
                             String word = entry.getWord();
                             String reverse = new StringBuilder(word).reverse()
                                                                     .toString();
                             return word.equals(reverse);
                         })
                         .sorted()
                         .collect(Collectors.toList());
    }

3. Add a method to the AggregatorController that consumes the list of Entries generated by your new service method created in step 2 above. To do this:

• Copy the method getDefinitionFor
• Change the @GetMapping path of your new method to /getAllPalindromes
• Remove the formal parameters from your new method (this endpoint doesn't take any user input).
• On the method header, change the return type to List<Entry>
• Change the service call to call the new service method created in step 2 above.

4. Test your new aggregator endpoint using a browser or Postman

• For extra credit, rewrite the palindrome service method to NOT use streams.
• You get to decide when/where to use loops, if-statements, etc...
• Method must return the same type (List<Entry>)
• You can use an array or whatever you want to generate an array of alpha characters to iterate over.
• Follow the pseudocode in the comments to come up with your own algorithm
• The ultimate idea is to create an algorithm that gets words that start and end with the same letter and combine them and determine which are palindromes.