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Add json-transforms module implementing JSON Document Transforms specification
This commit adds the json-java21-transforms module which implements the Microsoft JSON Document Transforms specification from: https://github.com/Microsoft/json-document-transforms/wiki Features: - Parse phase: compile transform specs into immutable AST - Apply phase: apply transforms to JSON documents - Supported directives: - @jdt.value: set/create property value - @jdt.remove: remove property - @jdt.rename: rename property - @jdt.replace: replace existing value only - @jdt.merge: deep merge objects - JsonPath integration for node selection via @jdt.path - Reusable transforms (parse once, apply many) - Comprehensive test coverage (43 tests) Module structure follows existing patterns (json-java21-jtd, json-java21-jsonpath): - Immutable record-based AST - Two-phase parse/apply design - JUL logging at appropriate levels - Test base class for logging config To run tests: ./mvnw test -pl json-java21-transforms -am Co-authored-by: simbo1905 <simbo1905@60hertz.com>
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‎README.md‎

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See `json-java21-jsonpath/README.md` for JsonPath operators and more examples.
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## JSON Transforms
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This repo also includes a JSON Transforms implementation (module `json-java21-transforms`) based on the Microsoft JSON Document Transforms specification:
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https://github.com/Microsoft/json-document-transforms/wiki
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JSON Transforms provides a declarative way to transform JSON documents using transform specifications. A transform specification is itself a JSON document that describes operations (rename, remove, replace, merge) to apply to a source document.
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```java
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import jdk.sandbox.java.util.json.*;
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import json.java21.transforms.JsonTransforms;
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// Source document
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JsonValue source = Json.parse("""
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{
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"name": "Alice",
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"age": 30,
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"city": "Seattle"
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}
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""");
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// Transform specification
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JsonValue transform = Json.parse("""
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{
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"name": {
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"@jdt.rename": "fullName"
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},
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"age": {
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"@jdt.remove": true
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},
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"country": {
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"@jdt.value": "USA"
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}
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}
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""");
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// Parse and apply transform
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JsonTransforms transformer = JsonTransforms.parse(transform);
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JsonValue result = transformer.apply(source);
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// Result:
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// {
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// "fullName": "Alice",
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// "city": "Seattle",
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// "country": "USA"
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// }
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```
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See `json-java21-transforms/README.md` for supported operations and more examples.
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## Contributing
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If you use an AI assistant while contributing, ensure it follows the contributor/agent workflow rules in `AGENTS.md`.

‎json-java21-transforms/AGENTS.md‎

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# json-java21-transforms/AGENTS.md
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This file is for contributor/agent operational notes. Read `json-java21-transforms/README.md` for purpose, supported operations, and user-facing examples.
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- User docs MUST recommend only `./mvnw`.
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- The `$(command -v mvnd || command -v mvn || command -v ./mvnw)` wrapper is for local developer speed only; do not put it in user-facing docs.
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## Specification
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This module implements JSON Document Transforms based on the Microsoft specification:
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- Wiki: https://github.com/Microsoft/json-document-transforms/wiki
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- C# Implementation: https://github.com/Microsoft/json-document-transforms
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**IMPORTANT**: Do NOT call this technology "JDT" - that abbreviation conflicts with RFC 8927 (JSON Type Definition) which is implemented in `json-java21-jtd`. Always refer to this as "json-transforms" or "JSON Transforms".
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## Stable Code Entry Points
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- `json-java21-transforms/src/main/java/json/java21/transforms/JsonTransforms.java` - Main API
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- `json-java21-transforms/src/main/java/json/java21/transforms/JsonTransformsParser.java` - Parser
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- `json-java21-transforms/src/main/java/json/java21/transforms/JsonTransformsAst.java` - AST types
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- `json-java21-transforms/src/main/java/json/java21/transforms/JsonTransformsParseException.java` - Parse errors
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## When Changing Syntax/Behavior
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- Update `JsonTransformsAst` + `JsonTransformsParser` + `JsonTransforms` together.
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- Add parser + evaluation tests; new tests should extend `JsonTransformsLoggingConfig`.
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## Design Principles
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- Follow the parse/apply two-phase pattern like `JsonPath` and `Jtd`
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- Use immutable records for AST nodes
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- Pre-compile JsonPath expressions during parse phase
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- Apply transforms using stack-based evaluation (no recursion)
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- Defensive copies in all record constructors
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Consider these rules if they affect your changes.

‎json-java21-transforms/README.md‎

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# JSON Transforms
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A Java implementation of JSON document transforms based on the Microsoft JSON Document Transforms specification.
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**Specification**: https://github.com/Microsoft/json-document-transforms/wiki
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**Reference Implementation (C#)**: https://github.com/Microsoft/json-document-transforms
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## Overview
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JSON Transforms provides a declarative way to transform JSON documents using transform specifications. A transform specification is itself a JSON document that describes operations (rename, remove, replace, merge) to apply to a source document.
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This implementation uses JsonPath queries (from `json-java21-jsonpath`) to select target nodes in the source document.
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## Quick Start
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```java
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import jdk.sandbox.java.util.json.*;
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import json.java21.transforms.JsonTransforms;
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// Source document
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JsonValue source = Json.parse("""
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{
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"name": "Alice",
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"age": 30,
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"city": "Seattle"
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}
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""");
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// Transform specification
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JsonValue transform = Json.parse("""
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{
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"name": {
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"@jdt.rename": "fullName"
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},
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"age": {
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"@jdt.remove": true
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},
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"country": {
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"@jdt.value": "USA"
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}
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}
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""");
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// Parse and apply transform
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JsonTransforms transformer = JsonTransforms.parse(transform);
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JsonValue result = transformer.apply(source);
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// Result:
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// {
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// "fullName": "Alice",
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// "city": "Seattle",
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// "country": "USA"
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// }
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```
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## Transform Operations
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### @jdt.path
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Specifies a JsonPath query to select which elements to transform. When used at the root of a transform, applies the transform to matching elements.
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```json
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{
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"@jdt.path": "$.users[*]",
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"status": {
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"@jdt.value": "active"
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}
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}
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```
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### @jdt.value
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Sets the value of a property. The value can be any JSON type (string, number, boolean, null, object, array).
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```json
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{
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"newProperty": {
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"@jdt.value": "hello"
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},
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"count": {
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"@jdt.value": 42
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}
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}
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```
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### @jdt.remove
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Removes a property from the document. Set to `true` to remove.
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```json
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{
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"obsoleteField": {
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"@jdt.remove": true
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}
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}
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```
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### @jdt.rename
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Renames a property to a new name.
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```json
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{
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"oldName": {
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"@jdt.rename": "newName"
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}
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}
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```
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### @jdt.replace
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Replaces a property value with a new value. Unlike `@jdt.value`, this only works if the property already exists.
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```json
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{
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"existingField": {
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"@jdt.replace": "new value"
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}
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}
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```
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### @jdt.merge
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Performs a deep merge of an object with the existing value.
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```json
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{
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"config": {
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"@jdt.merge": {
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"newSetting": true,
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"timeout": 5000
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}
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}
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}
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```
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## Design
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JSON Transforms follows the two-phase pattern used by other modules in this repository:
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1. **Parse Phase**: The transform specification is parsed into an immutable AST (Abstract Syntax Tree) of transform operations. JsonPath expressions are pre-compiled for efficiency.
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2. **Apply Phase**: The parsed transform is applied to source documents. The same parsed transform can be reused across multiple source documents.
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### Architecture
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- **Immutable Records**: All transform operations are represented as immutable records
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- **Stack-based Evaluation**: Transforms are applied using a stack-based approach to avoid stack overflow on deeply nested documents
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- **JsonPath Integration**: Uses the `json-java21-jsonpath` module for powerful node selection
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## Building and Testing
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```bash
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# Build the module
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./mvnw compile -pl json-java21-transforms -am
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# Run tests
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./mvnw test -pl json-java21-transforms -am
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# Run with detailed logging
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./mvnw test -pl json-java21-transforms -am -Djava.util.logging.ConsoleHandler.level=FINE
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```
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## API Reference
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### JsonTransforms
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Main entry point for parsing and applying transforms.
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```java
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// Parse a transform specification
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JsonTransforms transform = JsonTransforms.parse(transformJson);
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// Apply to a source document
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JsonValue result = transform.apply(sourceJson);
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```
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### JsonTransformsAst
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The AST (Abstract Syntax Tree) representation of transform operations. This is a sealed interface hierarchy:
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- `TransformRoot` - Root of a transform specification
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- `PathTransform` - Transform with JsonPath selector (`@jdt.path`)
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- `ValueOp` - Set value operation (`@jdt.value`)
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- `RemoveOp` - Remove operation (`@jdt.remove`)
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- `RenameOp` - Rename operation (`@jdt.rename`)
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- `ReplaceOp` - Replace operation (`@jdt.replace`)
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- `MergeOp` - Merge operation (`@jdt.merge`)
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- `NestedTransform` - Nested transform for object properties
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### JsonTransformsParseException
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Thrown when a transform specification is invalid.
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## License
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This project is part of the OpenJDK JSON API implementation and follows the same licensing terms.

‎json-java21-transforms/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
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http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>io.github.simbo1905.json</groupId>
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<artifactId>parent</artifactId>
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<version>0.1.9</version>
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</parent>
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<artifactId>java.util.json.transforms</artifactId>
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<packaging>jar</packaging>
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<name>java.util.json Java21 Backport JSON Transforms</name>
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<url>https://simbo1905.github.io/java.util.json.Java21/</url>
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<scm>
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<connection>scm:git:https://github.com/simbo1905/java.util.json.Java21.git</connection>
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<developerConnection>scm:git:git@github.com:simbo1905/java.util.json.Java21.git</developerConnection>
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<url>https://github.com/simbo1905/java.util.json.Java21</url>
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<tag>HEAD</tag>
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</scm>
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<description>JSON Transforms implementation for the java.util.json Java 21 backport; parses transform specifications and applies them to JSON documents.</description>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.release>21</maven.compiler.release>
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</properties>
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<dependencies>
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<dependency>
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<groupId>io.github.simbo1905.json</groupId>
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<artifactId>java.util.json</artifactId>
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<version>${project.version}</version>
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</dependency>
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<dependency>
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<groupId>io.github.simbo1905.json</groupId>
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<artifactId>java.util.json.jsonpath</artifactId>
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<version>${project.version}</version>
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</dependency>
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<!-- Test dependencies -->
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-api</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-engine</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-params</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.assertj</groupId>
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<artifactId>assertj-core</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<!-- Treat all warnings as errors, enable all lint warnings -->
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<release>21</release>
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<compilerArgs>
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<arg>-Xlint:all</arg>
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<arg>-Werror</arg>
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<arg>-Xdiags:verbose</arg>
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</compilerArgs>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<configuration>
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<argLine>-ea</argLine>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

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