Merge pull request modelcontextprotocol#312 from tzolov/mcp-0.9.0-updates

Add MCP Java SDK 0.9.0 updates

Author: markpollack

docs/development/updates.mdx

@@ -3,6 +3,13 @@ title: "What's New"
 description: 'The latest updates and improvements to MCP'
 ---
 
+<Update label="2025-04-10" description="Java SDK 0.9.0 released">
+- Version [0.9.0](https://github.com/modelcontextprotocol/java-sdk/releases/tag/v0.9.0) of the MCP Java SDK has been released.
+- Refactored logging system to use exchange mechanism
+- Custom Context Paths
+- Server Instructions
+- CallToolResult Enhancement   
+</Update>
 <Update label="2025-03-26" description="Kotlin SDK 0.4.0 released">
 - Fix issues and cleanup API
 - Added binary compatibility tracking to avoid breaking changes

docs/sdk/java/mcp-client.mdx

@@ -214,6 +214,28 @@ This capability allows:
 - Support for both text and image-based interactions
 - Optional inclusion of MCP server context in prompts
 
+
+### Logging Support
+
+The client can register a logging consumer to receive log messages from the server and set the minimum logging level to filter messages:
+
+```java	
+var mcpClient = McpClient.sync(transport)
+        .loggingConsumer(notification -> {
+            System.out.println("Received log message: " + notification.data());
+        })
+        .build();
+
+mcpClient.initialize();
+
+mcpClient.setLoggingLevel(McpSchema.LoggingLevel.INFO);
+
+// Call the tool that can sends logging notifications
+CallToolResult result = mcpClient.callTool(new McpSchema.CallToolRequest("logging-test", Map.of()));
+```
+Clients can control the minimum logging level they receive through the `mcpClient.setLoggingLevel(level)` request. Messages below the set level will be filtered out.
+Supported logging levels (in order of increasing severity): DEBUG (0), INFO (1), NOTICE (2), WARNING (3), ERROR (4), CRITICAL (5), ALERT (6), EMERGENCY (7)
+
 ## Using MCP Clients
 
 ### Tool Execution

docs/sdk/java/mcp-overview.mdx

@@ -145,7 +145,7 @@ Add the BOM to your project:
         <dependency>
             <groupId>io.modelcontextprotocol.sdk</groupId>
             <artifactId>mcp-bom</artifactId>
-            <version>0.8.1</version>
+            <version>0.9.0</version>
             <type>pom</type>
             <scope>import</scope>
         </dependency>
@@ -157,7 +157,7 @@ Add the BOM to your project:
   <Tab title="Gradle">
 ```groovy
 dependencies {
-  implementation platform("io.modelcontextprotocol.sdk:mcp-bom:0.8.1")
+  implementation platform("io.modelcontextprotocol.sdk:mcp-bom:0.9.0")
   //...
 }
 ```

docs/sdk/java/mcp-server.mdx

@@ -49,13 +49,6 @@ syncServer.addTool(syncToolSpecification);
 syncServer.addResource(syncResourceSpecification);
 syncServer.addPrompt(syncPromptSpecification);
 
-// Send logging notifications
-syncServer.loggingNotification(LoggingMessageNotification.builder()
-    .level(LoggingLevel.INFO)
-    .logger("custom-logger")
-    .data("Server initialized")
-    .build());
-
 // Close the server when done
 syncServer.close();
 ```
@@ -87,13 +80,6 @@ asyncServer.addPrompt(asyncPromptSpecification)
     .doOnSuccess(v -> logger.info("Prompt registered"))
     .subscribe();
 
-// Send logging notifications
-asyncServer.loggingNotification(LoggingMessageNotification.builder()
-    .level(LoggingLevel.INFO)
-    .logger("custom-logger")
-    .data("Server initialized")
-    .build());
-
 // Close the server when done
 asyncServer.close()
     .doOnSuccess(v -> logger.info("Server closed"))
@@ -526,6 +512,60 @@ The `CreateMessageRequest` object allows you to specify: `Content` - the input t
 `Model Preferences` - hints and priorities for model selection, `System Prompt` - instructions for the model's behavior and 
 `Max Tokens` - maximum length of the generated response.
 
+### Logging Support
+
+The server provides structured logging capabilities that allow sending log messages to clients with different severity levels. The
+ log notifications can only be sent from within an existing client session, such as tools, resources, and prompts calls.
+
+For example, we can send a log message from within a tool handler function. 
+On the client side, you can register a logging consumer to receive log messages from the server and set the minimum logging level to filter messages.
+
+```java	
+var mcpClient = McpClient.sync(transport)
+        .loggingConsumer(notification -> {
+            System.out.println("Received log message: " + notification.data());
+        })
+        .build();
+
+mcpClient.initialize();
+
+mcpClient.setLoggingLevel(McpSchema.LoggingLevel.INFO);
+
+// Call the tool that sends logging notifications
+CallToolResult result = mcpClient.callTool(new McpSchema.CallToolRequest("logging-test", Map.of()));
+```
+
+The server can send log messages using the `McpAsyncServerExchange`/`McpSyncServerExchange` object in the tool/resource/prompt handler function:
+
+```java
+var tool = new McpServerFeatures.AsyncToolSpecification(
+    new McpSchema.Tool("logging-test", "Test logging notifications", emptyJsonSchema),
+    (exchange, request) -> {  
+
+      exchange.loggingNotification( // Use the exchange to send log messages
+          McpSchema.LoggingMessageNotification.builder()
+            .level(McpSchema.LoggingLevel.DEBUG)
+            .logger("test-logger")
+            .data("Debug message")
+            .build())
+        .block();
+
+      return Mono.just(new CallToolResult("Logging test completed", false));
+    });
+
+var mcpServer = McpServer.async(mcpServerTransportProvider)
+  .serverInfo("test-server", "1.0.0")
+  .capabilities(
+    ServerCapabilities.builder()
+      .logging() // Enable logging support
+      .tools(true)
+      .build())
+  .tools(tool)
+  .build();
+```
+
+Clients can control the minimum logging level they receive through the `mcpClient.setLoggingLevel(level)` request. Messages below the set level will be filtered out.
+Supported logging levels (in order of increasing severity): DEBUG (0), INFO (1), NOTICE (2), WARNING (3), ERROR (4), CRITICAL (5), ALERT (6), EMERGENCY (7)
 
 ## Error Handling