# Interceptors

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Interceptors wrap inbound and outbound Temporal calls so you can apply shared behavior such as tracing, logging, or
authorization. See [Interceptors](/encyclopedia/interceptors) for the inbound vs outbound model.

Register them on the Client (`WorkflowClientOptions.Builder.setInterceptors`) or the Worker Factory
(`WorkerFactoryOptions.Builder.setWorkerInterceptors`). Full API:
[`io.temporal.common.interceptors`](https://www.javadoc.io/doc/io.temporal/temporal-sdk/latest/io/temporal/common/interceptors/package-summary.html).

Several interceptor APIs are marked `@Experimental`.

## Implement a Client interceptor

Extend `WorkflowClientInterceptorBase` and override `workflowClientCallsInterceptor` to return a
`WorkflowClientCallsInterceptor` that wraps `next`. Override only the calls you want to intercept; forward the rest to
`next` (or to `super`, if you extend `WorkflowClientCallsInterceptorBase`).

<!--SNIPSTART java-interceptors-client-interceptor-->
[java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/TracingClientInterceptor.java](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/TracingClientInterceptor.java)
```java
public class TracingClientInterceptor extends WorkflowClientInterceptorBase {
    @Override
    public WorkflowClientCallsInterceptor workflowClientCallsInterceptor(
        WorkflowClientCallsInterceptor next) {
        return new WorkflowClientCallsInterceptorBase(next) {
            @Override
            public WorkflowStartOutput start(WorkflowStartInput input) {
                System.out.println("starting workflow " + input.getWorkflowId());
                return super.start(input);
            }
        };
    }
}
```
<!--SNIPEND-->

Register the interceptor when you build the Client:

<!--SNIPSTART java-interceptors-register-client {"enable_code_dedenting": true}-->
[java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/RegisterInterceptors.java](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/RegisterInterceptors.java)
```java
WorkflowClientOptions clientOptions =
    WorkflowClientOptions.newBuilder().setInterceptors(new TracingClientInterceptor()).build();
WorkflowClient client = WorkflowClient.newInstance(service, clientOptions);
```
<!--SNIPEND-->

## Implement a Worker interceptor

Extend `WorkerInterceptorBase` and override `interceptWorkflow`, `interceptActivity`, or both, for the inbound call
chains you need. Each inbound interceptor must forward every override to `next`. To also intercept outbound calls made
from inside the Workflow, wrap the `WorkflowOutboundCallsInterceptor` passed to `init` and forward that wrapper to
`next.init(...)`:

<!--SNIPSTART java-interceptors-worker-interceptor-->
[java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/TracingWorkerInterceptor.java](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/TracingWorkerInterceptor.java)
```java
public class TracingWorkerInterceptor extends WorkerInterceptorBase {
    @Override
    public WorkflowInboundCallsInterceptor interceptWorkflow(WorkflowInboundCallsInterceptor next) {
        return new WorkflowInboundCallsInterceptorBase(next) {
            @Override
            public void init(WorkflowOutboundCallsInterceptor outboundCalls) {
                next.init(
                    new WorkflowOutboundCallsInterceptorBase(outboundCalls) {
                        @Override
                        public <R> ActivityOutput<R> executeActivity(ActivityInput<R> input) {
                            Workflow.getLogger(TracingWorkerInterceptor.class)
                                .info("starting activity " + input.getActivityName());
                            return super.executeActivity(input);
                        }
                    });
            }
        };
    }
}
```
<!--SNIPEND-->

Register the interceptor on the Worker Factory:

<!--SNIPSTART java-interceptors-register-worker {"enable_code_dedenting": true}-->
[java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/RegisterInterceptors.java](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/java-sandbox/workers/interceptors/src/main/java/io/temporal/docs/workers/interceptors/RegisterInterceptors.java)
```java
WorkerFactoryOptions factoryOptions =
    WorkerFactoryOptions.newBuilder().setWorkerInterceptors(new TracingWorkerInterceptor()).build();
WorkerFactory factory = WorkerFactory.newInstance(client, factoryOptions);
```
<!--SNIPEND-->

> **⚠️ Warning:**
> Workflow interceptors and replay
>
> Workflow interceptor methods also run during [replay](/develop/java/best-practices/testing-suite#replay). Use replay-safe
> APIs for logging, randomness, and time.
>

## Related

- [Observability - Tracing](/develop/java/platform/observability#tracing)
- [Error handling - Worker Interceptor](/develop/java/best-practices/error-handling#centralize-with-interceptor)
- [Spring Boot - Interceptors](/develop/java/integrations/spring-boot-integration#interceptors)
- [Plugins - Interceptors](/develop/plugins-guide#interceptors)