Refactor Network Analyser for Modularity and Performance by zhenyuefu · Pull Request #1 · zhenyuefu/NetworkAnalyser

zhenyuefu · 2026-02-12T08:10:17Z

This PR completely refactors the Network Analyser application to address performance issues, improve code modularity, and enhance the user interface.

Key Changes:

Architecture: Moved from a monolithic structure to a layered architecture (Model, Service, UI).
Model: Replaced the deep inheritance hierarchy (IPPacket extends EthernetPacket) with a composition-based approach where a Packet holds raw data and specific Header classes parse protocols on demand. This improves flexibility and correctness.
Parsing: Replaced the inefficient PacketAnalyser with a new HexDumpParser that reads files line-by-line and handles large files more gracefully.
UI:
- Performance: Used PacketViewModel for the TableView to efficiently display packet summaries.
- Responsiveness: Implemented background loading for file operations using JavaFX Task.
- Layout: Updated net.fxml to use BorderPane and SplitPane for a resizable and modern layout.
- Features: Added a Hex View to inspect raw packet bytes and a Status Bar for feedback.
Testing: Added unit tests for the parser and protocol header decoding to ensure correctness.

PR created automatically by Jules for task 4288025737854752343 started by @zhenyuefu

- Restructured project into `model`, `service`, `ui` packages. - Introduced `Packet` model with composition-based protocol headers (`EthernetHeader`, `IPHeader`, etc.) replacing inheritance. - Implemented `HexDumpParser` in `service` for robust and efficient file parsing. - Refactored UI to use `PacketViewModel` and `PacketTreeBuilder` for better separation of concerns and performance. - Added background file loading using `Task` to prevent UI freezing. - Enhanced UI with SplitPane layout, Hex View, and Status Bar. - Re-implemented Export functionality. - Added unit tests for parser and protocol headers. Co-authored-by: zhenyuefu <56567636+zhenyuefu@users.noreply.github.com>

google-labs-jules · 2026-02-12T08:10:18Z

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Changed `on: create` to `on: push` with `tags: ['*']`. The previous configuration triggered the release workflow on branch creation, which caused failures because `action-gh-release` expects a tag ref. This ensures the workflow only runs when a tag is pushed. Co-authored-by: zhenyuefu <56567636+zhenyuefu@users.noreply.github.com>

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Pull request overview

This PR refactors the Network Analyser into a more modular Model/Service/UI structure, replacing the prior inheritance-heavy packet model and parser with composition-based headers and a streaming hexdump parser, alongside a refreshed JavaFX UI (table + protocol tree + hex view + status bar).

Changes:

Introduces composition-based packet/header model (Packet, EthernetHeader, IPHeader, UDPHeader, DNSHeader, DHCPHeader).
Replaces parsing with HexDumpParser and adds unit tests for parsing and header decoding.
Updates JavaFX UI layout (net.fxml) and controller logic for background load/export plus new hex/status views.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
src/main/java/projectreseau/networkanalyser/MainController.java	Refactored controller to load/export in background, bind `TableView` to `PacketViewModel`, and populate tree + hex views.
src/main/resources/projectreseau/networkanalyser/net.fxml	Moves to `BorderPane`/`SplitPane` layout; adds hex view and status bar.
src/main/java/projectreseau/networkanalyser/service/HexDumpParser.java	New line-by-line hexdump parser producing `model.Packet` instances.
src/main/java/projectreseau/networkanalyser/ui/PacketViewModel.java	New view model deriving table fields from parsed headers.
src/main/java/projectreseau/networkanalyser/ui/PacketTreeBuilder.java	Builds protocol detail tree from headers for UI/export.
src/main/java/projectreseau/networkanalyser/model/Packet.java	New raw-packet container with id/length/data.
src/main/java/projectreseau/networkanalyser/model/EthernetHeader.java	Ethernet header decoding utilities.
src/main/java/projectreseau/networkanalyser/model/IPHeader.java	IPv4 header decoding utilities.
src/main/java/projectreseau/networkanalyser/model/UDPHeader.java	UDP header decoding utilities.
src/main/java/projectreseau/networkanalyser/model/DNSHeader.java	DNS header decoding utilities.
src/main/java/projectreseau/networkanalyser/model/DHCPHeader.java	DHCP/BOOTP header field accessors used for tree display.
src/test/java/projectreseau/networkanalyser/service/HexDumpParserTest.java	Tests parsing multiple packets from string input.
src/test/java/projectreseau/networkanalyser/model/ProtocolHeaderTest.java	Tests Ethernet and IPv4 header field decoding.

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Copilot · 2026-02-12T08:15:28Z

src/main/java/projectreseau/networkanalyser/ui/PacketViewModel.java

+        EthernetHeader eth = new EthernetHeader(packet.getData(), 0);
+        String p = eth.getTypeDescription();
+        String s = eth.getSourceMac();
+        String d = eth.getDestinationMac();
+        String i = "";
+
+        try {


The initial Ethernet parsing (getTypeDescription(), getSourceMac(), getDestinationMac()) happens before the try block. If the packet is truncated (< 14 bytes) this can throw and prevent the table from loading. Consider moving the Ethernet parsing inside the try (or validating length first) and falling back to safe defaults on failure.

Suggested change

EthernetHeader eth = new EthernetHeader(packet.getData(), 0);

String p = eth.getTypeDescription();

String s = eth.getSourceMac();

String d = eth.getDestinationMac();

String i = "";

try {

String p = "Unknown";

String s = "";

String d = "";

String i = "";

try {

EthernetHeader eth = new EthernetHeader(packet.getData(), 0);

p = eth.getTypeDescription();

s = eth.getSourceMac();

d = eth.getDestinationMac();

Copilot · 2026-02-12T08:15:29Z

src/main/java/projectreseau/networkanalyser/MainController.java

+        task.setOnSucceeded(e -> {
+            List<Packet> packets = task.getValue();
+            packetList.clear();
+            packetList.addAll(packets.stream().map(PacketViewModel::new).collect(Collectors.toList()));
+            if (statusLabel != null) statusLabel.setText("Loaded " + packets.size() + " packets from " + file.getName());
+        });


PacketViewModel instances are created in setOnSucceeded, which runs on the JavaFX Application Thread. For large captures, this will freeze the UI even though file parsing was offloaded. Consider doing the packets -> PacketViewModel transformation inside the Task.call() and only applying the final list to packetList on success.

Copilot · 2026-02-12T08:15:29Z

src/main/java/projectreseau/networkanalyser/MainController.java

+        Task<Void> task = new Task<>() {
+            @Override
+            protected Void call() throws Exception {
+                try (java.io.PrintWriter writer = new java.io.PrintWriter(file)) {
+                    for (PacketViewModel pvm : packetList) {
+                        Packet packet = pvm.getPacket();
+                        TreeItem<String> root = PacketTreeBuilder.build(packet);
+                        dumpTree(writer, root, "");
+                        writer.println();
+                        writer.println("--------------------------------------------------");
+                        writer.println();
                    }
                }


exportPackets iterates over packetList from the background Task thread. ObservableList is not thread-safe, and this can race with UI updates (or throw during iteration). Snapshot the current items on the FX thread before starting the task (e.g., copy to a plain List) and iterate over that snapshot in the background.

Copilot · 2026-02-12T08:15:29Z

src/main/java/projectreseau/networkanalyser/MainController.java

+        new Thread(task).start();
    }


Both loadPackets and exportPackets start raw Threads without setting them as daemon or using a managed executor. Non-daemon threads can keep the JVM alive after the window closes, and unmanaged threads make cancellation/lifecycle harder. Prefer an ExecutorService (or set thread name + daemon) and consider wiring Task cancellation to UI actions.

Copilot · 2026-02-12T08:15:30Z

src/main/java/projectreseau/networkanalyser/service/HexDumpParser.java

+        List<Packet> packets = new ArrayList<>();
+        int packetId = 1;
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        int expectedOffset = 0; // The next expected byte offset within the current packet
+


HexDumpParser uses an unbounded ByteArrayOutputStream for packet accumulation. If the input is malformed (missing a new packet offset) or extremely large, this can grow until OOM. Consider enforcing a maximum packet size (similar to the previous 64KiB snaplength) and terminating/starting a new packet or failing fast when exceeded.

Copilot · 2026-02-12T08:15:30Z

src/main/java/projectreseau/networkanalyser/service/HexDumpParser.java

+import java.util.ArrayList;
+import java.util.List;
+
+public class HexDumpParser {
+
+    public List<Packet> parse(File file) throws IOException {
+        try (BufferedReader reader = new BufferedReader(new FileReader(file))) {


parse(File) uses FileReader, which relies on the platform default charset. Since the project encoding is UTF-8, consider using an explicit charset (e.g., Files.newBufferedReader(..., UTF_8)) to avoid inconsistent behavior across machines.

Suggested change

import java.util.ArrayList;

import java.util.List;

public class HexDumpParser {

public List<Packet> parse(File file) throws IOException {

try (BufferedReader reader = new BufferedReader(new FileReader(file))) {

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.util.ArrayList;

import java.util.List;

public class HexDumpParser {

public List<Packet> parse(File file) throws IOException {

try (BufferedReader reader = Files.newBufferedReader(file.toPath(), StandardCharsets.UTF_8)) {

Copilot · 2026-02-12T08:15:30Z

src/main/java/projectreseau/networkanalyser/model/EthernetHeader.java

+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < 6; i++) {
+            if (i > 0) sb.append(":");
+            sb.append(String.format("%02x", bytes[pos + i]));


extractMac formats signed byte values with %02x, which can produce strings like ffffff8c for bytes >= 0x80. Mask each byte with & 0xFF (or otherwise convert to an unsigned int) before formatting so MAC addresses are always two hex digits per octet; this also makes ProtocolHeaderTest expectations pass.

Suggested change

sb.append(String.format("%02x", bytes[pos + i]));

sb.append(String.format("%02x", bytes[pos + i] & 0xFF));

Copilot · 2026-02-12T08:15:30Z

src/main/java/projectreseau/networkanalyser/MainController.java

+            for (int j = 0; j < 16; j++) {
+                if (i + j < data.length) {
+                    sb.append(String.format("%02x ", data[i + j]));
+                } else {
+                    sb.append("   ");
+                }
+                if (j == 7) sb.append(" ");
+            }


String.format("%02x", data[i + j]) formats a signed byte and can output ffffff8c-style values for bytes >= 0x80, which breaks the hex view. Convert the byte to an unsigned int (e.g., mask with & 0xFF) before formatting.

Copilot · 2026-02-12T08:15:31Z

src/main/java/projectreseau/networkanalyser/MainController.java

+
+            for (int j = 0; j < 16; j++) {
+                if (i + j < data.length) {
+                    sb.append(String.format("%02x ", data[i + j]));


This array access might be out of bounds, as the index might be equal to the array length + 14.

Copilot · 2026-02-12T08:15:31Z

src/main/java/projectreseau/networkanalyser/MainController.java

+
+            for (int j = 0; j < 16; j++) {
+                if (i + j < data.length) {
+                    char c = (char) (data[i + j] & 0xFF);


This array access might be out of bounds, as the index might be equal to the array length + 14.

Copilot AI review requested due to automatic review settings February 12, 2026 08:10

Copilot started reviewing on behalf of zhenyuefu February 12, 2026 08:10 View session

Copilot AI reviewed Feb 12, 2026

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Refactor Network Analyser for Modularity and Performance#1

Refactor Network Analyser for Modularity and Performance#1
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refactor/modular-network-analyzer-4288025737854752343

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	sb.append(String.format("%02x", bytes[pos + i]));
	sb.append(String.format("%02x", bytes[pos + i] & 0xFF));

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