HyperledgerFabric客户端开发五

这里介绍Chaincode的查询功能&＃xff0c; 从前面的介绍得知&＃xff0c; Fabric SDK提供了多种查询功能&＃xff0c; 具体包括Channel&＃xff0c; Block, Transaction, Chaincode 等信息&＃xff0c; 而这个功能&＃xff0c; 都是通过Channel对象实现的。

因此&＃xff0c; 首先创建channel对象。

// setup the fabric network
var channel &＃61; fabric_client.newChannel(&＃39;mychannel&＃39;);
var peer &＃61; fabric_client.newPeer(&＃39;grpc://localhost:7051&＃39;);
channel.addPeer(peer);


然后调用channel的方法实现相应的查询及其其他功能。例如使用queryByChaincode来查询Blockchain中存储的数据。

// queryCar chaincode function - requires 1 argument, ex: args: [&＃39;CAR4&＃39;],// queryAllCars chaincode function - requires no arguments , ex: args: [&＃39;&＃39;],const request &＃61; {//targets : --- letting this default to the peers assigned to the channelchaincodeId: &＃39;fabcar&＃39;,fcn: &＃39;queryAllCars&＃39;,args: [&＃39;&＃39;]};// send the query proposal to the peerreturn channel.queryByChaincode(request);
}).then((query_responses) &＃61;> {console.log("Query has completed, checking results");// query_responses could have more than one results if there multiple peers were used as targetsif (query_responses && query_responses.length &＃61;&＃61; 1) {if (query_responses[0] instanceof Error) {console.error("error from query &＃61; ", query_responses[0]);} else {console.log("Response is ", query_responses[0].toString());}} else {console.log("No payloads were returned from query");}


关于queryByChaincode方法的具体文档见&＃xff1a;Hyperledger Fabric SDK for node.js Class: Channel。其他关于Channel的文档见&＃xff1a; Hyperledger Fabric SDK for node.js Class: Channel 。

此外&＃xff0c; Channel 还提供了几个比较常用的用于查询的方法&＃xff1a;

queryBlock(blockNumber, target, useAdmin, skipDecode)

queryBlockByHash(block, target, useAdmin, skipDecode)

queryBlockByTxID(tx_id, target, useAdmin, skipDecode)

queryTransaction(tx_id, target, useAdmin, skipDecode)

queryInstantiatedChaincodes(target, useAdmin)

使用以上几个方法&＃xff0c; 可以帮助查看Blockchain的状态。