hyperledger fabric nodejs SDK开发（三）------SDK查询机制

SDK查询机制

async indexPage ( ctx ) { //异步函数indexPage

        const title = 'admin page' //设置一个title的常量

        let result = ''       //设置一个块变量result

        const body = ctx.request.body;  //获取传入请求的内容

      console.log(`request`,body.k0)   //打印出请求的内容k0 

        var fabric_client = new Fabric_Client(); //新建一个客户端实例

                  var key = "name"     //变量key，初值name

                  // setup the fabric network  启动fabric网络

                  var channel = fabric_client.newChannel('mychannel');  //发送消息到order来构建一个新的channel，命名为mychannel，返回一个空对象

                  var peer = fabric_client.newPeer('grpc://localhost:7051'); //创建一个新的节点

                  channel.addPeer(peer);  //将节点添加到通道

                  //设置成员变量为空

                  var member_user = null;

                  var store_path = path.join(os.homedir(), '.hfc-key-store'); //设置文件存储路径

                  console.log('Store path:'+store_path);  //打印文件存储路径

                  var tx_id = null;  //设置交易id为空

                  // create the key value store as defined in the fabric-client/config/default.json 'key-value-store' setting

       //设置加密材料的默认存储路径

                  result = await Fabric_Client.newDefaultKeyValueStore({ path: store_path

                  }).then((state_store) => { 

                      // assign the store to the fabric client //客户端设置存储路径

                      fabric_client.setStateStore(state_store);

                      var crypto_suite = Fabric_Client.newCryptoSuite();  //设置加密模块

                      // use the same location for the state store (where the users' certificate are kept)

                      // and the crypto store (where the users' keys are kept)  //客户端将密匙调用设置为该路径下

                      var crypto_store = Fabric_Client.newCryptoKeyStore({path: store_path});

                      crypto_suite.setCryptoKeyStore(crypto_store); //加密模块将生成密匙路径设置为同样路径

                      fabric_client.setCryptoSuite(crypto_suite);

            //检查用户1是否已经注册，这个用户信息从持久存储文件中获得，用户将签名所有的请求

                      // get the enrolled user from persistence, this user will sign all requests

                      return fabric_client.getUserContext('user1', true);

                  }).then((user_from_store) => {  //如果用户已经注册，则将用户设置为成员用户

                      if (user_from_store && user_from_store.isEnrolled()) {

                          console.log('Successfully loaded user1 from persistence');

                          member_user = user_from_store;

                      } else {  //否则再次注册

                          throw new Error('Failed to get user1.... run registerUser.js');

                      }

            //构建查询请求对象，四个参数，包括链码名称、交易id，调用函数、参数。

                      // queryTuna - requires 1 argument, ex: args: ['4'],

                      const request = {

                          chaincodeId: 'dateContract10',

                          txId: tx_id,

                          fcn: 'query',

                          args: [body.k0,body.k1]

                      };

            //将请求发送到指定对等节点，并由其对应的chaincode返回结果，所有的调用发送到invoke方法，同时在chaincode实现该方法，用字节数组返回结果。

                      // send the query proposal to the peer

                      return channel.queryByChaincode(request);

                  }).then((query_responses) => {  //得到查询结果，打印日志

                      console.log("Query has completed, checking results");

             //如果使用多个对等点作为目标，query_responses可以具有多个结果

                      // query_responses could have more than one  results if there multiple peers were used as targets

            //如果查询结果为一个，则

                      if (query_responses && query_responses.length == 1) {

                          if (query_responses[0] instanceof Error) { //如果查询结果继承了错误，则打印错误日志，结果为未获得数据

                              console.error("error from query = ", query_responses[0]);

                              result = "Could not locate tuna"

                          } else {  //否则打印出成功响应，且以string形式返回返回结果

                              console.log("Response is ", query_responses[0].toString());

                    return query_responses[0].toString()

                          }

                      } else {  //没有从查询返回有效响应

                          console.log("No payloads were returned from query");

                result = "Could not locate tuna"

                      }

                  }).catch((err) => {  //打印出错误，结果未查询失败

            console.error('Failed to query successfully :: ' + err);

            result = 'Failed to query successfully :: ' + err

           

                  });  //使用查询结果result和title，渲染query模板。

await ctx.render('query', {

            title,result

        })

     

},

流程：

与前端交互，获取前端输入内容，新建一个客户端实例，初始化网络，设置通道，节点，文件路径，加密材料存储路径，交易ID，构造请求参数，然后发送到背书节点，链码模拟执行，返回背书结果（字节数组），然后使用render渲染模板，实现前端更新。