Add langchain4j-interop: Spring AI 2.0 and LangChain4j 1.22 side by side

Same order assistant in both frameworks against a local fake OpenAI server: starter bean collision, wire differences, tool failure and loop bounds, observability meters, MCP-first tools, and a compile check of the 2025 article's snippets and Maven coordinates. Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01G8ikz8xdWuTP5yun8DZ1hk
2026-10-11 10:09:45 +00:00
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+# The same order assistant in Spring AI and in LangChain4j, one question: "Where is ORD-1001?"
+
+Spring AI : ChatClient.builder(model).defaultSystem(..).defaultTools(new SpringAiTools(orders))
+LangChain4j: AiServices.builder(Support.class).chatModel(model).tools(new Lc4jTools(orders))
+
+Spring AI answer    : Done: "Order ORD-1001: Status=SHIPPED, ETA=2026-10-14"
+LangChain4j answer  : Done: Order ORD-1001: Status=SHIPPED, ETA=2026-10-14
+HTTP requests sent  : Spring AI 2, LangChain4j 2.   Tool body executed: Spring AI 1, LangChain4j 1.
+
+What differs on the wire (computed from the four bodies below):
+  top-level fields   : Spring AI [messages, model, tools], LangChain4j [messages, model, stream, tools]
+  tool schema        : Spring AI has $schema=true additionalProperties=true; LangChain4j has $schema=false additionalProperties=false
+  tool result message: Spring AI sent "\"Order ORD-1001: Status=SHIPPED, ETA=2026-10-14\"", LangChain4j sent "Order ORD-1001: Status=SHIPPED, ETA=2026-10-14"
+
+--- Spring AI, request 1
+fields: [messages, model, tools]
+  system: "You are a customer support agent. Use the tools for order questions. Be concise."
+  user: "Where is ORD-1001?"
+  tool getOrderStatus - Get current order status by order ID params {"$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{"orderId":{"type":"string","description":"The unique identifier of the order"}},"required":["orderId"],"additionalProperties":false}
+
+--- Spring AI, request 2
+fields: [messages, model, tools]
+  system: "You are a customer support agent. Use the tools for order questions. Be concise."
+  user: "Where is ORD-1001?"
+  assistant: tool_call getOrderStatus {"orderId":"ORD-1001"}
+  tool: ""Order ORD-1001: Status=SHIPPED, ETA=2026-10-14""
+  tool getOrderStatus - Get current order status by order ID params {"$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{"orderId":{"type":"string","description":"The unique identifier of the order"}},"required":["orderId"],"additionalProperties":false}
+
+--- LangChain4j, request 1
+fields: [messages, model, stream, tools]
+  system: "You are a customer support agent. Use the tools for order questions. Be concise."
+  user: "Where is ORD-1001?"
+  tool getOrderStatus - Get current order status by order ID params {"type":"object","properties":{"orderId":{"type":"string","description":"The unique identifier of the order"}},"required":["orderId"]}
+
+--- LangChain4j, request 2
+fields: [messages, model, stream, tools]
+  system: "You are a customer support agent. Use the tools for order questions. Be concise."
+  user: "Where is ORD-1001?"
+  assistant: tool_call getOrderStatus {"orderId":"ORD-1001"}
+  tool: "Order ORD-1001: Status=SHIPPED, ETA=2026-10-14"
+  tool getOrderStatus - Get current order status by order ID params {"type":"object","properties":{"orderId":{"type":"string","description":"The unique identifier of the order"}},"required":["orderId"]}