opa-java-client

OPA java client is a wrapper for OPA REST API. The goal was to create client that is lightweight and framework independent. It's built for current Bisnode needs, including:

• creating documents
• creating policies
• querying for documents

Installation

Prerequisites: Java 11 or higher

Add library using maven:

<dependency>
    <groupId>com.bisnode.opa</groupId>
    <artifactId>opa-java-client</artifactId>
    <version>{version}</version>
</dependency>

or Gradle

implementation 'com.bisnode.opa:opa-java-client:{version}'

Usage

Our library is using Jackson for (de)serialization so, objects that you are passing/retrieving using this client should have either proper Jackson-friendly configuration or - the solution working in most cases - getters and setters for fields you want to pass/retrieve to/from OPA. More information about Jackson.

Query for document

OpaQueryApi client = OpaClient.builder()
                        .opaConfiguration("http://localhost:8181")
                        .build();

DesiredResponse response = client.queryForDocument(new QueryForDocumentRequest(yourDTO, "path/to/document"), DesiredResponse.class);

// Do whatever you like with the response

Query for a list of documents

This requires commons-lang3 to be present on your classpath.

OpaQueryApi client = OpaClient.builder()
        .opaConfiguration("http://localhost:8181")
        .build();
        
ParameterizedType type = TypeUtils.parameterize(List.class, DesiredResponse.class);
        
List<DesiredResponse> response = client.queryForDocument(new QueryForDocumentRequest(yourDTO, "path/to/document"), type);

// Do whatever you like with the response

####Example Example project is in examples/query-for-document directory.

Create policy

        OpaPolicyApi client = OpaClient.builder()
                                     .opaConfiguration("http://localhost:8181")
                                     .build();

        void createOrUpdatePolicy(new OpaPolicy("your_policy_id", "content of the policy"));

Create document

        OpaDataApi client = OpaClient.builder()
                                     .opaConfiguration("http://localhost:8181")
                                     .build();

        void createOrOverwriteDocument(new OpaDocument("path/to/document", "content of document (json)"));

Error handling

Error handling is done via exceptions. This means that if any error occurs, runtime exception which is subclass of OpaClientException is thrown. For now, there is simple error message returned.

OpaServerConnectionException is thrown when connection problems with OPA server occur.

Interface segregation

Every OPA (Data, Policy, Query) API has it's own interface. So, for example, if you want to use client only for querying, you can use OpaQueryApi as projection. Thanks to that, in your code there will be exposed only methods that are needed by you, while not allowing to mess with policies and data.

Available interface projections:

• OpaQueryApi
• OpaPolicyApi
• OpaDataApi

Developing and building

Build process and dependency management is done using Gradle. Tests are written in spock.

Contribution

Interested in contributing? Please, start by reading this document.