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feat: add size field and builder pattern to Resource record (#331)

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The size field helps hosts display file sizes and estimate context window usage.

- Add size parameter to Resource record for tracking raw content size in bytes
- Implement Builder pattern for Resource construction with validation
- Add deprecated constructor for backwards compatibility
- Add tests for builder pattern and field validation

Resolves #330

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>
This commit is contained in:
Luca Chang 2025-06-19 14:41:56 -07:00 • committed by Christian Tzolov
commit 6c330db5ad
3 changed files with 130 additions and 7 deletions
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64
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
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@ -29,6 +29,7 @@ import org.slf4j.LoggerFactory;
* Context Protocol Schema</a>.
*
* @author Christian Tzolov
* @author Luca Chang
*/
public final class McpSchema {
@ -482,6 +483,9 @@ public final class McpSchema {
* by clients to improve the LLM's understanding of available resources. It can be
* thought of like a "hint" to the model.
* @param mimeType The MIME type of this resource, if known.
* @param size The size of the raw resource content, in bytes (i.e., before base64
* encoding or any tokenization), if known. This can be used by Hosts to display file
* sizes and estimate context window usage.
* @param annotations Optional annotations for the client. The client can use
* annotations to inform how objects are used or displayed.
*/
@ -492,7 +496,67 @@ public final class McpSchema {
@JsonProperty("name") String name,
@JsonProperty("description") String description,
@JsonProperty("mimeType") String mimeType,
@JsonProperty("size") Long size,
@JsonProperty("annotations") Annotations annotations) implements Annotated {
/**
* @deprecated Only exists for backwards-compatibility purposes. Use
* {@link Resource#builder()} instead.
*/
@Deprecated
public Resource(String uri, String name, String description, String mimeType, Annotations annotations) {
this(uri, name, description, mimeType, null, annotations);
}
public static Builder builder() {
return new Builder();
}
public static class Builder {
private String uri;
private String name;
private String description;
private String mimeType;
private Long size;
private Annotations annotations;
public Builder uri(String uri) {
this.uri = uri;
return this;
}
public Builder name(String name) {
this.name = name;
return this;
}
public Builder description(String description) {
this.description = description;
return this;
}
public Builder mimeType(String mimeType) {
this.mimeType = mimeType;
return this;
}
public Builder size(Long size) {
this.size = size;
return this;
}
public Builder annotations(Annotations annotations) {
this.annotations = annotations;
return this;
}
public Resource build() {
Assert.hasText(uri, "uri must not be empty");
Assert.hasText(name, "name must not be empty");
return new Resource(uri, name, description, mimeType, size, annotations);
}
}
} // @formatter:on
/**

5
mcp/src/test/java/io/modelcontextprotocol/spec/ArgumentException.java Normal file
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@ -0,0 +1,5 @@
package io.modelcontextprotocol.spec;
public class ArgumentException {
}

72
mcp/src/test/java/io/modelcontextprotocol/spec/McpSchemaTests.java
View file

@ -3,23 +3,24 @@
*/
package io.modelcontextprotocol.spec;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.exc.InvalidTypeIdException;
import io.modelcontextprotocol.spec.McpSchema.TextResourceContents;
import net.javacrumbs.jsonunit.core.Option;
import org.junit.jupiter.api.Test;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.exc.InvalidTypeIdException;
import io.modelcontextprotocol.spec.McpSchema.TextResourceContents;
import net.javacrumbs.jsonunit.core.Option;
/**
* @author Christian Tzolov
@ -295,6 +296,59 @@ public class McpSchemaTests {
{"uri":"resource://test","name":"Test Resource","description":"A test resource","mimeType":"text/plain","annotations":{"audience":["user","assistant"],"priority":0.8}}"""));
}
@Test
void testResourceBuilder() throws Exception {
McpSchema.Annotations annotations = new McpSchema.Annotations(
Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
McpSchema.Resource resource = McpSchema.Resource.builder()
.uri("resource://test")
.name("Test Resource")
.description("A test resource")
.mimeType("text/plain")
.size(256L)
.annotations(annotations)
.build();
String value = mapper.writeValueAsString(resource);
assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
.isObject()
.isEqualTo(
json("""
{"uri":"resource://test","name":"Test Resource","description":"A test resource","mimeType":"text/plain","size":256,"annotations":{"audience":["user","assistant"],"priority":0.8}}"""));
}
@Test
void testResourceBuilderUriRequired() {
McpSchema.Annotations annotations = new McpSchema.Annotations(
Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
McpSchema.Resource.Builder resourceBuilder = McpSchema.Resource.builder()
.name("Test Resource")
.description("A test resource")
.mimeType("text/plain")
.size(256L)
.annotations(annotations);
assertThatThrownBy(resourceBuilder::build).isInstanceOf(java.lang.IllegalArgumentException.class);
}
@Test
void testResourceBuilderNameRequired() {
McpSchema.Annotations annotations = new McpSchema.Annotations(
Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
McpSchema.Resource.Builder resourceBuilder = McpSchema.Resource.builder()
.uri("resource://test")
.description("A test resource")
.mimeType("text/plain")
.size(256L)
.annotations(annotations);
assertThatThrownBy(resourceBuilder::build).isInstanceOf(java.lang.IllegalArgumentException.class);
}
@Test
void testResourceTemplate() throws Exception {
McpSchema.Annotations annotations = new McpSchema.Annotations(Arrays.asList(McpSchema.Role.USER), 0.5);