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codeboyzhoucursoragent
codeboyzhou
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cursoragent
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refactor: unify error handling across MCP component types
Centralize invocation and parameter conversion via ComponentInvocationSupport so tool, prompt, resource, and completion share the same sanitized error contract. Co-authored-by: Cursor <cursoragent@cursor.com>
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Lines changed: 131 additions & 30 deletions

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‎src/main/java/com/github/thought2code/mcp/annotated/reflect/ComponentInvocationSupport.java‎

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package com.github.thought2code.mcp.annotated.reflect;
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import com.github.thought2code.mcp.annotated.enums.McpServerError;
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import com.github.thought2code.mcp.annotated.exception.McpServerException;
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import com.github.thought2code.mcp.annotated.server.converter.AbstractParameterConverter;
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import io.modelcontextprotocol.spec.McpSchema;
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import java.lang.reflect.Method;
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import java.util.List;
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import java.util.Map;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* Shared invocation flow for MCP server components (tool, prompt, resource, completion).
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*
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* <p>Centralizes parameter conversion and method invocation so all component types apply the same
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* sanitized error contract from {@link MethodInvoker}.
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*
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* @author codeboyzhou
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*/
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public final class ComponentInvocationSupport {
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private static final Logger log = LoggerFactory.getLogger(ComponentInvocationSupport.class);
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private ComponentInvocationSupport() {}
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/**
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* Converts request arguments and invokes the target method.
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*
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* @param instance component instance
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* @param method target method
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* @param parameterConverter converter for annotated parameters
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* @param arguments request arguments
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* @return invocation result, including sanitized errors from conversion or method failures
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*/
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public static Invocation invokeWithParameters(
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Object instance,
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Method method,
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AbstractParameterConverter<?> parameterConverter,
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Map<String, Object> arguments) {
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MethodMetadata metadata = MethodMetadata.of(method);
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try {
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List<Object> params = parameterConverter.convertAll(metadata.getParameters(), arguments);
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return MethodInvoker.invoke(instance, method, metadata, params);
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} catch (RuntimeException e) {
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return parameterConversionFailure(e);
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}
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}
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/**
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* Invokes a no-argument component method.
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*
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* @param instance component instance
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* @param method target method
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* @return invocation result
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*/
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public static Invocation invoke(Object instance, Method method) {
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return MethodInvoker.invoke(instance, method, MethodMetadata.of(method));
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}
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/**
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* Invokes a completion handler method.
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*
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* @param instance component instance
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* @param method target method
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* @param argument completion argument from the request
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* @return invocation result
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*/
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public static Invocation invoke(
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Object instance, Method method, McpSchema.CompleteRequest.CompleteArgument argument) {
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MethodMetadata metadata = MethodMetadata.of(method);
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return MethodInvoker.invoke(instance, method, metadata, argument);
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}
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private static Invocation parameterConversionFailure(RuntimeException e) {
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log.error("Parameter conversion failed", e);
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return Invocation.builder()
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.result(McpServerError.METHOD_INVOCATION_ERROR.toString())
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.isError(true)
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.build();
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}
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/**
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* Throws {@link McpServerException} when the invocation failed.
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*
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* @param invocation invocation to check
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*/
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public static void throwIfError(Invocation invocation) {
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if (invocation.isError()) {
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throw new McpServerException(invocation.result().toString());
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}
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}
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/**
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* Returns the invocation result when successful.
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*
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* @param invocation invocation to check
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* @param type expected result type
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* @param <T> result type
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* @return typed invocation result
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* @throws McpServerException when the invocation failed
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*/
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@SuppressWarnings("unchecked")
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public static <T> T requireResult(Invocation invocation, Class<T> type) {
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throwIfError(invocation);
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return (T) invocation.result();
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}
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}

‎src/main/java/com/github/thought2code/mcp/annotated/reflect/Invocation.java‎

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@@ -17,6 +17,11 @@ public static Builder builder() {
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return new Builder();
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}
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/** Returns the invocation result as text. */
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public String asText() {
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return result.toString();
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}
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/**
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* This class implements the builder pattern for creating a new instance of {@code
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* InvocationResult}.

‎src/main/java/com/github/thought2code/mcp/annotated/server/component/McpServerCompletion.java‎

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@@ -4,9 +4,8 @@
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import com.github.thought2code.mcp.annotated.annotation.McpPromptCompletion;
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import com.github.thought2code.mcp.annotated.annotation.McpResourceCompletion;
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import com.github.thought2code.mcp.annotated.exception.McpServerComponentRegistrationException;
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import com.github.thought2code.mcp.annotated.reflect.ComponentInvocationSupport;
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import com.github.thought2code.mcp.annotated.reflect.Invocation;
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import com.github.thought2code.mcp.annotated.reflect.MethodInvoker;
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import com.github.thought2code.mcp.annotated.reflect.MethodMetadata;
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import io.modelcontextprotocol.server.McpServerFeatures;
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import io.modelcontextprotocol.spec.McpSchema;
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import java.lang.reflect.Method;
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private static McpSchema.CompleteResult invoke(
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Object instance, Method method, McpSchema.CompleteRequest request) {
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MethodMetadata metadata = MethodMetadata.of(method);
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McpSchema.CompleteRequest.CompleteArgument argument = request.argument();
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Invocation invocation = MethodInvoker.invoke(instance, method, metadata, argument);
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McpCompleteCompletion completion = (McpCompleteCompletion) invocation.result();
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Invocation invocation = ComponentInvocationSupport.invoke(instance, method, request.argument());
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McpCompleteCompletion completion =
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ComponentInvocationSupport.requireResult(invocation, McpCompleteCompletion.class);
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return new McpSchema.CompleteResult(
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new McpSchema.CompleteResult.CompleteCompletion(
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completion.values(), completion.total(), completion.hasMore()));

‎src/main/java/com/github/thought2code/mcp/annotated/server/component/McpServerPrompt.java‎

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import com.github.thought2code.mcp.annotated.annotation.McpPrompt;
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import com.github.thought2code.mcp.annotated.annotation.McpPromptParam;
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import com.github.thought2code.mcp.annotated.enums.ServerType;
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import com.github.thought2code.mcp.annotated.reflect.ComponentInvocationSupport;
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import com.github.thought2code.mcp.annotated.reflect.Invocation;
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import com.github.thought2code.mcp.annotated.reflect.MethodInvoker;
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import com.github.thought2code.mcp.annotated.reflect.MethodMetadata;
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import com.github.thought2code.mcp.annotated.server.converter.McpPromptParameterConverter;
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import com.github.thought2code.mcp.annotated.util.JacksonHelper;
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import com.github.thought2code.mcp.annotated.util.StringHelper;
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import java.lang.reflect.Parameter;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Map;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import reactor.core.publisher.Mono;
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log.debug("Handling MCP GetPromptRequest: {}", JacksonHelper.toJsonString(request));
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MethodMetadata metadata = MethodMetadata.of(method);
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Parameter[] parameters = metadata.getParameters();
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Map<String, Object> arguments = request.arguments();
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List<Object> params = parameterConverter.convertAll(parameters, arguments);
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Invocation invocation = MethodInvoker.invoke(instance, method, metadata, params);
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Invocation invocation =
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ComponentInvocationSupport.invokeWithParameters(
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instance, method, parameterConverter, request.arguments());
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McpSchema.Content content =
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McpSchema.TextContent.builder(invocation.result().toString()).build();
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McpSchema.Content content = McpSchema.TextContent.builder(invocation.asText()).build();
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McpSchema.PromptMessage message =
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McpSchema.PromptMessage.builder(McpSchema.Role.USER, content).build();
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McpSchema.GetPromptResult getPromptResult =

‎src/main/java/com/github/thought2code/mcp/annotated/server/component/McpServerResource.java‎

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import com.github.thought2code.mcp.annotated.McpApplicationContext;
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import com.github.thought2code.mcp.annotated.annotation.McpResource;
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import com.github.thought2code.mcp.annotated.enums.ServerType;
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import com.github.thought2code.mcp.annotated.reflect.ComponentInvocationSupport;
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import com.github.thought2code.mcp.annotated.reflect.Invocation;
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import com.github.thought2code.mcp.annotated.reflect.MethodInvoker;
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import com.github.thought2code.mcp.annotated.reflect.MethodMetadata;
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import com.github.thought2code.mcp.annotated.util.JacksonHelper;
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import com.github.thought2code.mcp.annotated.util.StringHelper;
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import io.modelcontextprotocol.server.McpAsyncServer;
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log.debug("Handling ReadResourceResult request: {}", JacksonHelper.toJsonString(resource));
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MethodMetadata metadata = MethodMetadata.of(method);
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Invocation invocation = MethodInvoker.invoke(instance, method, metadata);
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Invocation invocation = ComponentInvocationSupport.invoke(instance, method);
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final String uri = resource.uri();
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final String mimeType = resource.mimeType();
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final String text = invocation.result().toString();
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final String text = invocation.asText();
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McpSchema.ResourceContents contents =
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McpSchema.TextResourceContents.builder(uri, text).mimeType(mimeType).build();
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McpSchema.ReadResourceResult readResourceResult =

‎src/main/java/com/github/thought2code/mcp/annotated/server/component/McpServerTool.java‎

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import com.github.thought2code.mcp.annotated.annotation.McpToolParam;
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import com.github.thought2code.mcp.annotated.enums.JavaTypeToJsonSchemaMapper;
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import com.github.thought2code.mcp.annotated.enums.ServerType;
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import com.github.thought2code.mcp.annotated.reflect.ComponentInvocationSupport;
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import com.github.thought2code.mcp.annotated.reflect.Invocation;
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import com.github.thought2code.mcp.annotated.reflect.MethodInvoker;
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import com.github.thought2code.mcp.annotated.reflect.MethodMetadata;
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import com.github.thought2code.mcp.annotated.server.McpStructuredContent;
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import com.github.thought2code.mcp.annotated.server.converter.McpToolParameterConverter;
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import com.github.thought2code.mcp.annotated.util.JacksonHelper;
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log.debug("Handling MCP CallToolRequest: {}", JacksonHelper.toJsonString(request));
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183-
MethodMetadata metadata = MethodMetadata.of(method);
184-
Parameter[] parameters = metadata.getParameters();
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Map<String, Object> arguments = request.arguments();
186-
List<Object> params = parameterConverter.convertAll(parameters, arguments);
187-
Invocation invocation = MethodInvoker.invoke(instance, method, metadata, params);
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Invocation invocation =
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ComponentInvocationSupport.invokeWithParameters(
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instance, method, parameterConverter, request.arguments());
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189186
Object result = invocation.result();
190-
String textContent = result.toString();
187+
String textContent = invocation.asText();
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Object structuredContent = Map.of();
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193-
if (result instanceof McpStructuredContent mcpStructuredContent) {
190+
if (!invocation.isError() && result instanceof McpStructuredContent mcpStructuredContent) {
194191
textContent = mcpStructuredContent.asTextContent();
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structuredContent = mcpStructuredContent;
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}

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