# 在web3j中使用Infura

[ConsenSys](https://consensys.net/)提供了[Infura](https://infura.io/)服务,这使以太坊客户端运行在云商，那样你不需要自己搭建以太坊。

当你注册这个服务的时候，你会获取到一个token来连接到相应的以太坊网络:

以太坊主链：

<https://mainnet.infura.io/>

以太坊测试网络(Rinkeby)

<https://rinkeby.infura.io/>

以太坊测试网络(Kovan)

<https://kovan.infura.io/>

以太坊测试网络(Ropsten)

<https://ropsten.infura.io/>

为了获取一些在这些网络中使用的以太币，你可以参考[Ethereum testnets](https://docs.web3j.io/transactions.html#ethereum-testnets)。

## InfuraHttpClient

web3j的infura模块提供了一个Infura HTTP客户端，这支持了Infura特定的`Infura-Ethereum-Preferred-Client`头。这允许你去指定是否需要一个Geth或者Parity客户端去回应你的请求。你可以创建客户端就像常规的HTTPClient:

```java
Web3j web3 = Web3j.build(new HttpService("https://rinkeby.infura.io/<your-token>"));
Web3ClientVersion web3ClientVersion = web3.web3ClientVersion().send();
System.out.println(web3ClientVersion.getWeb3ClientVersion());
```

如果你想要去测试Infura的JSON-RPC调用，更新[CoreIT](https://github.com/web3j/web3j/blob/master/integration-tests/src/test/java/org/web3j/protocol/core/CoreIT.java)为你的URL并运行它。

你可以通过[Infura docs](https://github.com/INFURA/infura/blob/master/docs/source/index.html.md#choosing-a-client-to-handle-your-request)来获取更多信息。

## 交易

为了和Infura节点交易，你需要去创建并且在你发送之前进行离线签名交易，Infura节点无法看到你的加密的以太坊密钥文件，这需要通过你的私人Geth/Parity私有的管理命令来解锁。

你可以在[离线交易签名](https://docs.web3j.io/transactions.html#offline-signing)和[管理API](https://docs.web3j.io/transactions.html#offline-signing)章节中获取更多信息。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://watermelon.gitbook.io/web3j/zai-web3j-zhong-shi-yong-infura.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.