Campus Print Queue with Java Microservices: A 2027 Project Guide

A student print-desk volunteer needs a trustworthy answer to a small operational question: how many pages were printed for each document type? This Java Microservices project turns that question into a service contract and failure lab. The useful result is a traceable decision rule, a clear output and evidence that a change behaves as expected.

This is a 2027 study-edition project brief. All example records and operational situations are fictional. Start with basic Java Microservices knowledge, the ability to inspect structured data and a local practice environment. The complete first version should answer the stated question before adding accounts, real integrations or additional screens.

Define the project rule

Printed page count records completed output. Cancelled or merely queued jobs must not contribute, and duplex printing needs a separate sheet-count definition if added later. For this exercise, one row represents one print_job. The stable key is record_id; document_type is the grouping or filtering label. The numeric page_count field uses pages. Accepted states are queued, printed, cancelled.

The summary selects status printed and applies sum to the selected numeric values. Keep this definition visible in the interface, response or report so another learner can reproduce it. Use positive finite values in the starter fixture and define any future zero or missing-value policy explicitly.

Choose the Java Microservices approach

Begin with two small services only when a boundary is useful: one owns the record and the other consumes its summary. State which service is authoritative and what a timeout means. Compare this split with a single service so complexity remains a deliberate trade-off. Record correlation identifiers and design duplicate handling before adding retries.

The three design decisions to explain in your project notes are:

• One owner for each piece of data. Apply this choice to print_job records and explain its effect on page_count.
• Timeouts and bounded retries. Apply this choice to print_job records and explain its effect on page_count.
• Contract compatibility. Apply this choice to print_job records and explain its effect on page_count.

Work through a small sample

The three records below are deliberately small enough to inspect by hand. They are a compact specification for the data shape and expected result, and can later be expanded into a larger synthetic fixture.

[
  {
    "record_id": "print-queue-01",
    "document_type": "Workshop Handout",
    "page_count": 25,
    "status": "printed",
    "recorded_on": "2027-01-04"
  },
  {
    "record_id": "print-queue-02",
    "document_type": "Project Report",
    "page_count": 40,
    "status": "queued",
    "recorded_on": "2027-01-05"
  },
  {
    "record_id": "print-queue-03",
    "document_type": "Practice Worksheet",
    "page_count": 15,
    "status": "printed",
    "recorded_on": "2027-01-06"
  }
]

Only the first and third records match printed. Their page_count values are 25 and 15; the full-fixture result is 40 pages, with 2 matching records. Selecting document_type = Workshop Handout leaves the first record, so the result becomes 25 pages, with 1 match. This provides two independent checks for the filter and aggregation.

The full-fixture output contract is:

{
  "matching_count": 2,
  "operation": "sum",
  "value": 40,
  "unit": "pages"
}

Check the result by document_type

The overall figure answers the all-records version of the question. Grouping by document_type produces the following separate expectations, using the same printed rule. The middle group has a record in the source fixture but no qualifying observation.

Use this breakdown when answering the group-level question. Compare like-for-like units and keep the matching count visible, especially for averages. A different filter changes which records enter the calculation; it does not change the meaning of the metric.

The code blocks describe sample data and an expected result. Implement the surrounding feature using the installed version of your chosen tools, then save the actual run evidence separately from these expectations.

Build the feature in three passes

1. Describe the request contract

Define a read operation for the print_job collection and an optional document_type filter. Document accepted status values and the positive numeric page_count field. Decide how the client receives validation details before implementing a write operation.

2. Place the rule in a service

Calculate the sum for printed records inside a request-independent function. Keep persistence access separate. Return a count, value and pages label so a consumer can distinguish an empty set from an actual measured result.

3. Verify the stored outcome

Start with the fixture, execute one controlled change, and read it back. A rejected update must leave the collection unchanged. If the application uses memory only, document its restart behaviour instead of implying that the data is durable.

Find the mistake before polishing the result

A useful defect to introduce deliberately is: Page count is labelled sheet count without considering duplex output. First reproduce it against the fixture, then identify the smallest rule or state transition that explains the mismatch. Fix that boundary and rerun the full-fixture and selected-label examples. This creates a stronger explanation than changing several unrelated parts until the screen looks right.

The scenario-specific acceptance check is: Keep page and sheet measures distinct and label the displayed unit. Preserve before-and-after evidence. Add a missing document_type, a negative page_count, an unrecognised status and a duplicate record_id as separate invalid cases. Define the rejection or duplicate-handling policy before testing, and verify that invalid input does not silently change valid existing records.

Check the Java Microservices concerns as well:

• A downstream timeout needs a visible outcome.
• A duplicate request must not double the change.
• A consumer must tolerate an added optional field.

For an empty filter match, the expected sum value is 0. Keep matching_count at zero. This distinction prevents an empty dataset from being interpreted as a measured observation.

Explain the finished work in a portfolio

Show the student print-desk volunteer question, the record definition and the expected calculation first. Then demonstrate a document_type filter and the acceptance check. Include the fixture, setup instructions, chosen tool versions, actual test output and one remaining limitation in the repository. If you show a screenshot, pair it with the input that produced it. Another learner should be able to repeat the same result from a clean checkout.

For a focused extension, add a second document_type selection and compare the two groups using the same rule. Specify how missing groups appear and keep the original fixture as a regression case. Expand scope only after the current calculation, state handling and recovery path remain understandable.

Questions learners often ask

Which print_job records belong in the result?

Select records whose status is exactly printed and that satisfy the chosen document_type filter. Other states remain in the source data and can have separate summaries. Follow the domain rule above when a record changes state.

What should happen when no records match?

Return a zero total with a matching count of zero and a clear empty-result message. Keep the applied filter visible so the user can change it. Avoid using a loading indicator for a completed request that simply has no matching data.

How can I prove the page_count result is correct?

Reconcile the first and third sample records, then repeat the calculation for Workshop Handout alone. Save both expected and actual outputs, and rerun the scenario-specific acceptance check after making a change.

Continue learning with Groot Academy

Use this exercise as a concrete discussion point when choosing a learning path. Explore the related Groot Academy course and ask about the current syllabus, learning mode and project practice. Course availability and batch details should be confirmed directly with the academy.

For implementation details, consult the official Java Microservices documentation matching the tools you install. This project defines an original practice brief; it does not depend on a forecast about 2027 software releases.

Continue with Campus Parcel Desk using Java Microservices, or compare Campus Print Queue using ASP.NET Core. These companion practice guides are part of the 2027 learning collection.