json_demo

JSON Serialization Demo

This example demonstrates how to use JSON marshaling and unmarshaling with ClassAds.

Features Demonstrated

1. Marshal ClassAd to JSON - Convert a ClassAd into JSON format
2. Expression Serialization - See how expressions are serialized with the special \/Expr(<expression>)\/ format
3. Lists and Nested ClassAds - Handle complex nested structures
4. Unmarshal JSON to ClassAd - Convert JSON back into a ClassAd
5. Round-trip Serialization - Verify that marshal→unmarshal preserves data

JSON Format

The ClassAd JSON serialization follows these rules:

• Simple literals (integers, reals, strings, booleans) → JSON values
• undefined → JSON null
• Lists → JSON arrays
• Nested ClassAds → JSON objects
• Complex expressions → Special format: "/Expr(<expression>)/" (appears as "\/Expr(<expression>)\/" in JSON due to / escaping)

Expression Format Example

A ClassAd like:

[x = 5; y = x + 3]

Serializes to JSON as:

{
  "x": 5,
  "y": "\/Expr(x + 3)\/"
}

The format is /Expr(...)/) where the forward slashes are escaped in JSON as \/.

When unmarshaled back, the expression x + 3 is preserved and will correctly evaluate to 8 in the context of the ClassAd.

Running the Demo

go run main.go

Sample Output

The demo shows:

• Simple value serialization
• Expression handling with the special format
• Lists of both values and expressions
• Nested ClassAds as JSON objects
• JSON-to-ClassAd unmarshaling with expression evaluation
• Round-trip verification

Use Cases

This JSON serialization is useful for:

• REST APIs - Send/receive ClassAds over HTTP
• Configuration files - Store ClassAds in JSON format
• Interoperability - Exchange ClassAds with non-Go systems
• Database storage - Store ClassAds in JSON columns
• Logging - Serialize ClassAds for structured logging