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How to validate fields of a bidirectional grpc streaming api on every new part, just not on the stream.
You are building a bidirectional gRPC streaming API and need to ensure that each part of the stream (every individual message) is validated before it’s processed. This validation needs to occur continuously throughout the stream, not just when the stream is first initiated.
Please fine the proto message below validating content value
Creating a Protobuf Message below


syntax = "proto3";

message ChatMessage {
    string user_id = 1;       // User ID for identifying the sender
    string content = 2[
    (google.api.field_behavior) = REQUIRED,
    (buf.validate.field).int32.gte = 1,
    (buf.validate.field).int32.lte = 10000
  ];                          // Content of the message
    int64 timestamp = 3;      // Timestamp of the message
}

service ChatService {
    rpc ChatStream(stream ChatMessage) returns (stream ChatMessage);
}

But the buf.validate.field will only validate content value in the stream request (part I)
For any further parts ( I, II, III) the validation will not work since its applied on stream request and not on each part. 
s each message in the stream arrives, you want to make sure that it adheres to certain rules or constraints. This means that instead of validating all messages at once (at the beginning of the stream), each message needs to be validated as it arrives. This ensures that only valid data is processed, while invalid messages can be rejected or flagged immediately.

Data Constraints: For example, in the case of a chat application, you might want to validate that:

The user ID is not null and matches a specific format (e.g., alphanumeric, 3-20 characters). The content of the message is not empty and doesn’t exceed a maximum length (e.g., 500 characters). The timestamp is a valid Unix timestamp (not in the future or too old).

How to validate fields of a bidirectional grpc streaming api on every new part, just not on the stream.
You are building a bidirectional gRPC streaming API and need to ensure that each part of the stream (every individual message) is validated before it’s processed. This validation needs to occur continuously throughout the stream, not just when the stream is first initiated.
Please fine the proto message below validating content value
Creating a Protobuf Message below


syntax = "proto3";

message ChatMessage {
    string user_id = 1;       // User ID for identifying the sender
    string content = 2[
    (google.api.field_behavior) = REQUIRED,
    (buf.validate.field).int32.gte = 1,
    (buf.validate.field).int32.lte = 10000
  ];                          // Content of the message
    int64 timestamp = 3;      // Timestamp of the message
}

service ChatService {
    rpc ChatStream(stream ChatMessage) returns (stream ChatMessage);
}

But the buf.validate.field will only validate content value in the stream request (part I)
For any further parts ( I, II, III) the validation will not work since its applied on stream request and not on each part. 
s each message in the stream arrives, you want to make sure that it adheres to certain rules or constraints. This means that instead of validating all messages at once (at the beginning of the stream), each message needs to be validated as it arrives. This ensures that only valid data is processed, while invalid messages can be rejected or flagged immediately.

Data Constraints: For example, in the case of a chat application, you might want to validate that:

The user ID is not null and matches a specific format (e.g., alphanumeric, 3-20 characters). The content of the message is not empty and doesn’t exceed a maximum length (e.g., 500 characters). The timestamp is a valid Unix timestamp (not in the future or too old).

• streaming
• grpc
• bidirectional
• proto3
• javax.validation

Share Improve this question Follow asked Feb 4 at 7:38 ShinchanShinchan 4377 bronze badges

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1 Answer 1

Sorted by: Reset to default 0

Enters : javax.validation

javax.validation in Java is the standard validation framework used for validating Java beans (POJOs), and you can integrate it into your gRPC service logic to perform field-level validation during the streaming process.

**step 1:**  Setting Up javax.validation

    <dependency>
    <groupId>javax.validation</groupId>
    <artifactId>javax.validation-api</artifactId>
    <version>2.0.1.Final</version>
</dependency>

<dependency>
    <groupId>.hibernate</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>6.0.13.Final</version> <!-- Choose the version that suits you -->
</dependency>


**step 2:**
Since you’ll use javax.validation, the gRPC generated POJOs will work, but you may want to create a Java class that corresponds to the ChatMessage to apply validation annotations. This is usually a wrapper class.

    import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.validation.constraints.Pattern;
import java.io.Serializable;

public class ChatMessageWrapper implements Serializable {
    
    @NotNull(message = "User ID cannot be null")
    @Pattern(regexp = "[A-Za-z0-9_-]{3,20}", message = "User ID must be alphanumeric and between 3-20 characters")
    private String userId;
    
    @NotNull(message = "Content cannot be null")
    @Size(min = 1, max = 500, message = "Content must be between 1 and 500 characters")
    private String content;
    
    @NotNull(message = "Timestamp cannot be null")
    private Long timestamp;

    // Getters and setters
    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Long getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(Long timestamp) {
        this.timestamp = timestamp;
    }
}
**step 3:**
Server-side Validation Logic (Bidirectional Streaming)

    import io.grpc.stub.StreamObserver;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import java.util.Set;

public class ChatServiceImpl extends ChatServiceGrpc.ChatServiceImplBase {
    
    private final Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

    @Override
    public StreamObserver<ChatMessage> chatStream(StreamObserver<ChatMessage> responseObserver) {
        return new StreamObserver<ChatMessage>() {

            @Override
            public void onNext(ChatMessage chatMessage) {
                // Validate each incoming ChatMessage
                ChatMessageWrapper wrapper = new ChatMessageWrapper();
                wrapper.setUserId(chatMessage.getUserId());
                wrapper.setContent(chatMessage.getContent());
                wrapper.setTimestamp(chatMessage.getTimestamp());

                Set<ConstraintViolation<ChatMessageWrapper>> violations = validator.validate(wrapper);

                // If there are validation errors, we can send an error response
                if (!violations.isEmpty()) {
                    for (ConstraintViolation<ChatMessageWrapper> violation : violations) {
                        System.out.println("Validation error: " + violation.getMessage());
                    }
                    // Optionally, respond with an error message
                    responseObserver.onNext(ChatMessage.newBuilder()
                        .setUserId("Server")
                        .setContent("Validation failed.")
                        .setTimestamp(System.currentTimeMillis())
                        .build());
                    responseObserver.onCompleted();
                    return;
                }

                // If the message is valid, process the message
                // For now, just echo the message back to the client
                responseObserver.onNext(chatMessage);
            }

            @Override
            public void onError(Throwable t) {
                // Handle stream error (e.g., client disconnects)
                t.printStackTrace();
            }

            @Override
            public void onCompleted() {
                // Handle stream completion
                responseObserver.onCompleted();
            }
        };
    }
}


bidirectional streaming in gRPC, you want to validate each part of the stream individually. Since each message that flows in the stream needs to be validated before it’s processed, you can do this in the server’s ChatStream method on onNext()

Performance consideration: Keep in mind that validating every part of the stream can introduce overhead. You might want to optimize this by performing validation checks on fields that are critical or applying them conditionally based on business logic.

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