# jsonrpc4j

**Repository Path**: qkl-repo/jsonrpc4j

## Basic Information

- **Project Name**: jsonrpc4j
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 1
- **Created**: 2021-02-07
- **Last Updated**: 2022-08-05

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# JSON-RPC for Java

This project aims to provide the facility to easily implement
JSON-RPC for the java programming language.  jsonrpc4j uses the
[Jackson][Jackson page] library to convert java
objects to and from json objects (and other things related to
JSON-RPC).

[![Javadoc](https://img.shields.io/badge/javadoc-OK-blue.svg)](http://briandilley.github.io/jsonrpc4j/javadoc/1.5.0/)
[![Download](https://img.shields.io/maven-central/v/com.github.briandilley.jsonrpc4j/jsonrpc4j.svg) ](https://repo1.maven.org/maven2/com/github/briandilley/jsonrpc4j/jsonrpc4j/1.5.3/)
[![Travis CI](https://travis-ci.org/gaborbernat/jsonrpc4j.svg?branch=master)](https://travis-ci.org/gaborbernat/jsonrpc4j)
[![GitHub commits](https://img.shields.io/github/commits-since/briandilley/jsonrpc4j/1.5.3.svg)](https://github.com/briandilley/jsonrpc4j/compare/1.5.3...master)
[![Maintenance](https://img.shields.io/maintenance/yes/2018.svg)](https://github.com/briandilley/jsonrpc4j/commits/master)

## Features Include:
  * Streaming server (`InputStream` \ `OutputStream`)
  * HTTP Server (`HttpServletRequest` \ `HttpServletResponse`)
  * Portlet Server (`ResourceRequest` \ `ResourceResponse`)
  * Socket Server (`StreamServer`)
  * Integration with the Spring Framework (`RemoteExporter`)
  * Streaming client
  * HTTP client
  * Dynamic client proxies
  * Annotations support
  * Custom error resolving
  * Composite services

## Maven
This project is built with [Maven][Maven page]. Be
sure to check the pom.xml for the dependencies if you're not using
maven.  If you're already using spring you should have most (if not all)
of the dependencies already - outside of maybe the
[Jackson Library][Jackson page].  Jsonrpc4j is available
from the maven central repo. Add the following to your pom.xml if you're
using maven:


In `<dependencies>`:

```xml
	<!-- jsonrpc4j -->
	<dependency>
		<groupId>com.github.briandilley.jsonrpc4j</groupId>
		<artifactId>jsonrpc4j</artifactId>
		<version>1.6</version>
	</dependency>
```

or with gradle:

```groovy
    implementation('com.github.briandilley.jsonrpc4j:jsonrpc4j:1.6')
```

If you want to just download the projects output JAR and it's dependencies you can
do it over at the [Maven repository][Maven repository].

## JSON-RPC specification
The official source for the [JSON-RPC 2.0 specification][JSON RPC Spec].
The guys over at [json-rpc google group][Google Group]
seem to be fairly active, so you can ask clarifying questions there.

## Streaming server and client
Jsonrpc4j comes with a streaming server and client to support applications of all types
(not just HTTP).  The `JsonRpcClient` and `JsonRpcServer` have simple methods
that take `InputStream`s and `OutputStream`s.  Also in the library is a `JsonRpcHttpClient`
which extends the `JsonRpcClient` to add HTTP support.

## Spring Framework
jsonrpc4j provides a `RemoteExporter` to expose java services as JSON-RPC over HTTP without
requiring any additional work on the part of the programmer.  The following example explains
how to use the `JsonServiceExporter` within the Spring Framework.

Create your service interface:

```java
package com.mycompany;
public interface UserService {
    User createUser(String userName, String firstName, String password);
    User createUser(String userName, String password);
    User findUserByUserName(String userName);
    int getUserCount();
}
```

Implement it:

```java
package com.mycompany;
public class UserServiceImpl
    implements UserService {

    public User createUser(String userName, String firstName, String password) {
        User user = new User();
        user.setUserName(userName);
        user.setFirstName(firstName);
        user.setPassword(password);
        database.saveUser(user);
        return user;
    }

    public User createUser(String userName, String password) {
        return this.createUser(userName, null, password);
    }

    public User findUserByUserName(String userName) {
        return database.findUserByUserName(userName);
    }

    public int getUserCount() {
        return database.getUserCount();
    }

}
```

Configure your service in spring as you would any other RemoteExporter:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
		http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

    <bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/>

    <bean id="userService" class="com.mycompany.UserServiceImpl">
    </bean>

    <bean name="/UserService.json" class="com.googlecode.jsonrpc4j.spring.JsonServiceExporter">
        <property name="service" ref="userService"/>
        <property name="serviceInterface" value="com.mycompany.UserService"/>
    </bean>

</beans>
```

Your service is now available at the URL /UserService.json.  Type conversion of
JSON->Java and Java->JSON will happen for you automatically.  This service can
be accessed by any JSON-RPC capable client, including the `JsonProxyFactoryBean`,
`JsonRpcClient` and `JsonRpcHttpClient` provided by this project:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean  class="com.googlecode.jsonrpc4j.spring.JsonProxyFactoryBean">
        <property name="serviceUrl" value="http://example.com/UserService.json"/>
        <property name="serviceInterface" value="com.mycompany.UserService"/>
    </bean>

<beans>
```

In the case that your JSON-RPC requires named based parameters rather than indexed
parameters an annotation can be added to your service interface (this also works on
the service implementation for the ServiceExporter):

```java
package com.mycompany;
public interface UserService {
    User createUser(@JsonRpcParam(value="theUserName") String userName, @JsonRpcParam(value="thePassword") String password);
}
```

By default all error message responses contain the the message as returned by
Exception.getmessage() with a code of 0.  This is not always desirable.
jsonrpc4j supports annotated based customization of these error messages and
codes, for example:

```java
package com.mycompany;
public interface UserService {
    @JsonRpcErrors({
        @JsonRpcError(exception=UserExistsException.class,
            code=-5678, message="User already exists", data="The Data"),
        @JsonRpcError(exception=Throwable.class,code=-187)
    })
    User createUser(@JsonRpcParam(value="theUserName") String userName, @JsonRpcParam(value="thePassword") String password);
}
```

The previous example will return the error code `-5678` with the message
`User already exists` if the service throws a UserExistsException.  In the
case of any other exception the code `-187` is returned with the value
of `getMessage()` as returned by the exception itself.

### Auto Discovery With Annotations

Spring can also be configured to auto-discover services and clients with annotations.

To configure auto-discovery of annotated services first annotate the service interface:

```java
@JsonRpcService("/path/to/MyService")
interface MyService {
... service methods ...
}
```

Next annotate the implementation of the service interface;

```java
@AutoJsonRpcServiceImpl
class MyServiceImpl {
... service methods' implementations ...
}
```

and use the following configuration to allow spring to find the implementation that you would like to expose:

```xml
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

  <bean class="com.googlecode.jsonrpc4j.spring.AutoJsonRpcServiceImplExporter"/>

  <bean class="com.mycompany.MyServiceImpl" />

</beans>
```

Configuring a client is just as easy:

```xml
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

  <bean class="com.googlecode.jsonrpc4j.spring.AutoJsonRpcClientProxyCreator">
    <property name="baseUrl" value="http://hostname/api/" />
    <property name="scanPackage" value="com.mycompany.services" />
  </bean>

</beans>
```

Where the `baseUrl` is added to the front of the path value provided by the
`JsonRpcService` annotation and `scanPackage` tells spring which packages
to scan for services.

## Without the Spring Framework
jsonrpc4j can be used without the spring framework as well.  In fact, the client
and server both work in an Android environment.

### Client
Here's an example of how to use the client to communicate with the JSON-RPC service described above:

```java
JsonRpcHttpClient client = new JsonRpcHttpClient(
    new URL("http://example.com/UserService.json"));

User user = client.invoke("createUser", new Object[] { "bob", "the builder" }, User.class);
```

Or, the ProxyUtil class can be used in conjunction with the interface to create a dynamic proxy:

```java
JsonRpcHttpClient client = new JsonRpcHttpClient(
    new URL("http://example.com/UserService.json"));

UserService userService = ProxyUtil.createClientProxy(
    getClass().getClassLoader(),
    UserService.class,
    client);

User user = userService.createUser("bob", "the builder");
```

### server
The server can be used without spring as well:

```java
// create it
JsonRpcServer server = new JsonRpcServer(userService, UserService.class);
```

After having created the server it's simply a matter of calling one of the
`handle(...)` methods available.  For example, here's a servlet using the
very same `UserService`:

```java
class UserServiceServlet
    extends HttpServlet {

    private UserService userService;
    private JsonRpcServer jsonRpcServer;

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        jsonRpcServer.handle(req, resp);
    }

    public void init(ServletConfig config) {
        //this.userService = ...
        this.jsonRpcServer = new JsonRpcServer(this.userService, UserService.class);
    }

}
```

### Composite Services
Multiple services can be combined into a single server using one of the
`ProxyUtil::createCompositeService(...)` methods.  For example:

```java
UserverService userService = ...;
ContentService contentService = ...;
BlackJackService blackJackService = ...;

Object compositeService = ProxyUtil.createCompositeServiceProxy(
    this.getClass().getClassLoader(),
    new Object[] { userService, contentService, blackJackService},
    new Class<?>[] { UserService.class, ContentService.class, BlackJackService.class},
    true);

// now compositeService can be used as any of the above service, ie:
User user = ((UserverService)compositService).createUser(...);
Content content =  ((ContentService)compositService).getContent(...);
Hand hand = ((BlackJackService)compositService).dealHand(...);

```

This can be used in conjunction with the `JsonRpcServer` to expose the service
methods from all services at a single location:

```java
JsonRpcServer jsonRpcServer = new JsonRpcServer(compositeService);
```

A spring service exporter exists for creating composite services as well
named `CompositeJsonServiceExporter`.

### Streaming (Socket) Server
A streaming server that uses `Socket`s is available in the form of the
`StreamServer` class.  It's use is very straightforward:

```java
// create the jsonRpcServer
JsonRpcServer jsonRpcServer = new JsonRpcServer(...);

// create the stream server
int maxThreads = 50;
int port = 1420;
InetAddress bindAddress = InetAddress.getByName("...");
StreamServer streamServer = new StreamServer(
    jsonRpcServer, maxThreads, port, bindAddress);

// start it, this method doesn't block
streamServer.start();
```

and when you're ready to shut the server down:

```java
// stop it, this method blocks until
// shutdown is complete
streamServer.stop();
```

Of course, this is all possible in the Spring Framework as well:

```xml
    <bean id="streamingCompositeService" class="com.googlecode.jsonrpc4j.spring.CompositeJsonStreamServiceExporter">
        <!-- can be an IP, hostname or omitted to listen on all available devices -->
        <property name="hostName" value="localhost"/>
        <property name="port" value="6420"/>
        <property name="services">
        	<list>
	        	<ref bean="userService" 	/>
	        	<ref bean="contentService" 	/>
	        	<ref bean="blackJackService" 	/>
        	</list>
        </property>
    </bean>
```
	}


### `JsonRpcServer` settings explained
The following settings apply to both the `JsonRpcServer` and `JsonServiceExporter`:

  * `allowLessParams` - Boolean specifying whether or not the server should allow for methods to be invoked by clients supplying less than the required number of parameters to the method.
  * `allowExtraParams` - Boolean specifying whether or not the server should allow for methods to be invoked by clients supplying more than the required number of parameters to the method.
  * `rethrowExceptions` - Boolean specifying whether or not the server should re-throw exceptions after sending them back to the client.
  * `backwardsComaptible` - Boolean specifying whether or not the server should allow for jsonrpc 1.0 calls.  This only includes the omission of the jsonrpc property of the request object, it will not enable class hinting.
  * `errorResolver` - An implementation of the `ErrorResolver` interface that resolves exception thrown by services into meaningful responses to be sent to clients.  Multiple `ErrorResolver`s can be configured using the `MultipleErrorResolver` implementation of this interface.
  * `batchExecutorService` - A configured `ExecutorService` to use for parallel JSON-RPC batch processing. By default batch requests are handled sequentially.

### Server Method resolution
Methods are resolved in the following way, each step immediately short circuits the
process when the available methods is 1 or less.

  1. If a method has the @JsonRpcMethod annotation, then if the annotation value has the same name as the request method, it is considered.  If the annotation has `required` set to `true`, then the Java method name is not considered.
  2. Otherwise, all methods with the same name as the request method are considered.
  3. If `allowLessParams` is disabled methods with more parameters than the request are removed
  4. If `allowExtraParams` is disabled then methods with less parameters than the request are removed
  5. If either of the two parameters above are enabled then methods with the lowest difference in parameter count from the request are kept
  6. Parameters types are compared to the request parameters and the method(s) with the highest number of matching parameters is kept
  7. If there are multiple methods remaining then the first of them are used

jsonrpc4j's method resolution allows for overloaded methods _sometimes_.  Primitives are
easily resolved from json to java.  But resolution between other objects are not possible.


For example, the following overloaded methods will work just fine:

json request:

```json
{"jsonrpc":"2.0", "id":"10", "method":"aMethod", "params":["Test"]}
```

java methods:

```java
public void aMethod(String param1);
public void aMethod(String param1, String param2);
public void aMethod(String param1, String param2, int param3);
```

But the following will not:

json request:

```json
{"jsonrpc":"2.0", "id":"10", "method":"addFriend", "params":[{"username":"example", "firstName":"John"}]}
```

java methods:

```java
public void addFriend(UserObject userObject);
public void addFriend(UserObjectEx userObjectEx);
```

The reason being that there is no efficient way for the server to
determine the difference in the json between the `UserObject`
and `UserObjectEx` Plain Old Java Objects.

#### Custom method names

In some instances, you may need to expose a JsonRpc method that is not a valid Java method name.
In this case, use the annotation @JsonRpcMethod on the service method.  You may also use this annotation
to disambiguate overloaded methods by setting the `required` property on the annotation to `true`.

```java
@JsonRpcService("/jsonrpc")
public interface LibraryService {
    @JsonRpcMethod("VideoLibrary.GetTVShows")
    List<TVShow> fetchTVShows(@JsonRpcParam(value="properties") final List<String> properties);
}
```

```json
{"jsonrpc":"2.0", "method": "VideoLibrary.GetTVShows", "params": { "properties": ["title"] }, "id":1}
```

[Google Group]: http://groups.google.com/group/json-rpc
[Jackson page]: https://github.com/FasterXML/jackson
[JSON RPC Spec]: http://www.jsonrpc.org/specification
[Maven page]: http://maven.apache.org
[Maven repository]: http://mvnrepository.com/artifact/com.github.briandilley.jsonrpc4j/jsonrpc4j