diff --git a/build.gradle b/build.gradle
index d6e854f..395f82a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -65,7 +65,6 @@ protobuf {
             artifact = 'io.grpc:protoc-gen-grpc-java:' + grpc_java_version
         }
     }
-   // generatedFilesBaseDir = "$projectDir/src"
     generateProtoTasks {
         all().each { task ->
             task.plugins {
diff --git a/src/main/java/org/bdware/bdledger/api/grpc/Client.java b/src/main/java/org/bdware/bdledger/api/grpc/Client.java
new file mode 100644
index 0000000..4c8cd5f
--- /dev/null
+++ b/src/main/java/org/bdware/bdledger/api/grpc/Client.java
@@ -0,0 +1,752 @@
+package org.bdware.bdledger.api.grpc;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.protobuf.ByteString;
+import com.google.protobuf.Empty;
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.Metadata;
+import io.grpc.StatusRuntimeException;
+import io.grpc.stub.MetadataUtils;
+import org.bdware.bdledger.api.grpc.pb.CommonProto.TransactionType;
+import org.bdware.bdledger.api.grpc.pb.LedgerGrpc;
+import org.bdware.bdledger.api.grpc.pb.LedgerProto.*;
+import org.bdware.bdledger.api.grpc.pb.NodeGrpc;
+import org.bdware.bdledger.api.grpc.pb.NodeProto.ClientVersionResponse;
+import org.bdware.bdledger.api.grpc.pb.QueryGrpc;
+import org.bdware.bdledger.api.grpc.pb.QueryProto.*;
+
+import java.time.ZonedDateTime;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * 事务账本客户端
+ *
+ * <p>如有更灵活的需求可直接使用{@link org.bdware.bdledger.api.grpc.pb.LedgerGrpc}类。
+ *
+ * @author nex
+ * @see <a href="#">事务账本API</a>
+ */
+public class Client {
+
+  private static final Logger logger = Logger.getLogger(Client.class.getName());
+
+  private ManagedChannel channel;
+  private NodeGrpc.NodeFutureStub nodeFutureStub;
+  private NodeGrpc.NodeBlockingStub nodeBlockingStub;
+  private LedgerGrpc.LedgerFutureStub ledgerFutureStub;
+  private LedgerGrpc.LedgerBlockingStub ledgerBlockingStub;
+  private QueryGrpc.QueryFutureStub queryFutureStub;
+  private QueryGrpc.QueryBlockingStub queryBlockingStub;
+//    private final ManagedChannel channel;
+//    private final NodeGrpc.NodeFutureStub nodeFutureStub;
+//    private final NodeGrpc.NodeBlockingStub nodeBlockingStub;
+//    private final LedgerGrpc.LedgerFutureStub ledgerFutureStub;
+//    private final LedgerGrpc.LedgerBlockingStub ledgerBlockingStub;
+//    private final QueryGrpc.QueryFutureStub queryFutureStub;
+//    private final QueryGrpc.QueryBlockingStub queryBlockingStub;
+
+  /**
+   * 构造客户端来向{@code host:port} BDLedger节点发请求。
+   */
+  public Client(String host, int port) {
+    this(ManagedChannelBuilder.forAddress(host, port).usePlaintext(), null);
+  }
+
+  /**
+   * 构造客户端，使用{@code token}作access token来向{@code host:port} BDLedger节点发请求。
+   */
+  public Client(String host, int port, String token) {
+    this(ManagedChannelBuilder.forAddress(host, port).usePlaintext(), token);
+  }
+
+  /**
+   * 用已有的{@link io.grpc.Channel}对象构造客户端来向BDLedger节点发请求。
+   */
+  public Client(ManagedChannelBuilder<?> channelBuilder, String token) {
+    channel = channelBuilder.build();
+
+    nodeFutureStub = NodeGrpc.newFutureStub(channel);
+    nodeBlockingStub = NodeGrpc.newBlockingStub(channel);
+    ledgerFutureStub = LedgerGrpc.newFutureStub(channel);
+    ledgerBlockingStub = LedgerGrpc.newBlockingStub(channel);
+    queryFutureStub = QueryGrpc.newFutureStub(channel);
+    queryBlockingStub = QueryGrpc.newBlockingStub(channel);
+
+    if (token != null) {
+      Metadata fixedHeaders = new Metadata();
+      fixedHeaders.put(Metadata.Key.of("authorization", Metadata.ASCII_STRING_MARSHALLER), "bearer " + token);
+      nodeFutureStub = GrpcHeaderInterceptor.attachHeaders(nodeFutureStub, fixedHeaders);
+      nodeBlockingStub = GrpcHeaderInterceptor.attachHeaders(nodeBlockingStub, fixedHeaders);
+      ledgerFutureStub = GrpcHeaderInterceptor.attachHeaders(ledgerFutureStub, fixedHeaders);
+      ledgerBlockingStub = GrpcHeaderInterceptor.attachHeaders(ledgerBlockingStub, fixedHeaders);
+      queryFutureStub = GrpcHeaderInterceptor.attachHeaders(queryFutureStub, fixedHeaders);
+      queryBlockingStub = GrpcHeaderInterceptor.attachHeaders(queryBlockingStub, fixedHeaders);
+    }
+  }
+
+  /**
+   * 关闭客户端的网络连接。
+   */
+  public void shutdown() throws InterruptedException {
+    channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
+  }
+
+  /**
+   * <a
+   * href="#">查询BDLedger节点版本</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<ClientVersionResponse> clientVersion() {
+
+    info("*** clientVersion");
+
+    try {
+      return nodeFutureStub.clientVersion(Empty.getDefaultInstance());
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">查询BDLedger节点版本</a>
+   * （阻塞）
+   */
+  public ClientVersionResponse clientVersionSync() {
+
+    info("*** clientVersionSync");
+
+    try {
+      return nodeBlockingStub.clientVersion(Empty.getDefaultInstance());
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  /**
+   * <a href="#">创建账本</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<CreateLedgerResponse> createLedger(String name) {
+
+    info("*** createLedger: name={0}", name);
+
+    try {
+      return ledgerFutureStub.createLedger(createLedgerRequest(name));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a href="#">创建账本</a>
+   * （阻塞）
+   */
+  public CreateLedgerResponse createLedgerSync(String name) {
+
+    info("*** createLedgerSync: name={0}", name);
+
+    try {
+      return ledgerBlockingStub.createLedger(createLedgerRequest(name));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private CreateLedgerRequest createLedgerRequest(String name) {
+    return CreateLedgerRequest.newBuilder().setName(name).build();
+  }
+
+  /**
+   * <a href="#">返回账本列表</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetLedgersResponse> getLedgers() {
+
+    info("*** getLedgers");
+
+    try {
+      return ledgerFutureStub.getLedgers(Empty.getDefaultInstance());
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a href="#">返回账本列表</a>
+   * （阻塞）
+   */
+  public GetLedgersResponse getLedgersSync() {
+
+    info("*** getLedgersSync");
+
+    try {
+      return ledgerBlockingStub.getLedgers(Empty.getDefaultInstance());
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">发送新事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<SendTransactionResponse> sendTransaction(
+      String ledger, TransactionType type, String from, long nonce, String to, byte[] data) {
+
+    info(
+        "*** sendTransaction: ledger={0} type={1} from={2} to={3} data={4}",
+        ledger, type, from, to, data);
+
+    try {
+      return ledgerFutureStub.sendTransaction(SendTransactionRequest(ledger, type, from, nonce, to, data));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">发送新事务</a>
+   * （阻塞）
+   */
+  public SendTransactionResponse sendTransactionSync(
+      String ledger, TransactionType type, String from, long nonce, String to, byte[] data) {
+
+    info(
+        "*** sendTransactionSync: ledger={0} type={1} from={2} to={3} data={4}",
+        ledger, type, from, to, data);
+
+    try {
+      return ledgerBlockingStub.sendTransaction(SendTransactionRequest(ledger, type, from, nonce, to, data));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private SendTransactionRequest SendTransactionRequest(
+      String ledger, TransactionType type, String from, long nonce, String to, byte[] data) {
+
+    SendTransactionRequest.Transaction.Builder txBuilder =
+        SendTransactionRequest.Transaction.newBuilder().setType(type);
+    if (from != null) {
+      txBuilder.setFrom(ByteString.copyFrom(Utils.hexStringToByteArray(from)));
+    }
+    txBuilder.setNonce(nonce);
+    if (to != null) {
+      txBuilder.setTo(ByteString.copyFrom(Utils.hexStringToByteArray(to)));
+    }
+    if (data != null) {
+      txBuilder.setData(ByteString.copyFrom(data));
+    }
+
+    return SendTransactionRequest.newBuilder().setLedger(ledger).setTransaction(txBuilder).build();
+  }
+
+  /**
+   * <a
+   * href="#">返回哈希所指定的区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlockByHashResponse> getBlockByHash(
+      String ledger, String hash, boolean fullTransactions) {
+
+    info(
+        "*** getBlockByHash: ledger={0} hash={1} fullTransactions={2}",
+        ledger, hash, fullTransactions);
+
+    try {
+      return queryFutureStub.getBlockByHash(getBlockByHashRequest(ledger, hash, fullTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回哈希所指定的区块</a>
+   * （阻塞）
+   */
+  public GetBlockByHashResponse getBlockByHashSync(String ledger, String hash, boolean fullTransactions) {
+
+    info(
+        "*** getBlockByHashSync: ledger={0} hash={1} fullTransactions={2}",
+        ledger, hash, fullTransactions);
+
+    try {
+      return queryBlockingStub.getBlockByHash(getBlockByHashRequest(ledger, hash, fullTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private GetBlockByHashRequest getBlockByHashRequest(
+      String ledger, String hash, boolean fullTransactions) {
+
+    GetBlockByHashRequest.Builder reqBuilder =
+        GetBlockByHashRequest.newBuilder().setLedger(ledger).setFullTransactions(fullTransactions);
+    if (hash != null) {
+      reqBuilder.setHash(ByteString.copyFrom(Utils.hexStringToByteArray(hash)));
+    }
+
+    return reqBuilder.build();
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlocksResponse> getBlocks(String ledger, ZonedDateTime startDateTime, IncludeTransactions includeTransactions) {
+    return getBlocks(ledger, startDateTime.toEpochSecond(), includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlocksResponse> getBlocks(String ledger, ZonedDateTime startDateTime, ZonedDateTime endDateTime, IncludeTransactions includeTransactions) {
+    return getBlocks(ledger, startDateTime.toEpochSecond(), endDateTime.toEpochSecond(), includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （阻塞）
+   */
+  public GetBlocksResponse getBlocksSync(String ledger, ZonedDateTime startDateTime, IncludeTransactions includeTransactions) {
+    return getBlocksSync(ledger, startDateTime.toEpochSecond(), includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （阻塞）
+   */
+  public GetBlocksResponse getBlocksSync(String ledger, ZonedDateTime startDateTime, ZonedDateTime endDateTime, IncludeTransactions includeTransactions) {
+    return getBlocksSync(ledger, startDateTime.toEpochSecond(), endDateTime.toEpochSecond(), includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlocksResponse> getBlocks(String ledger, long startUnixTime, IncludeTransactions includeTransactions) {
+    return getBlocks(ledger, startUnixTime, -1, includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlocksResponse> getBlocks(String ledger, long startUnixTime, long endUnixTime, IncludeTransactions includeTransactions) {
+
+    info(
+        "*** getBlocks: ledger={0} startUnixTime={1} endUnixTime={2}",
+        ledger, startUnixTime, endUnixTime);
+
+    try {
+      return queryFutureStub.getBlocks(blocksRequest(ledger, startUnixTime, endUnixTime, includeTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （阻塞）
+   */
+  public GetBlocksResponse getBlocksSync(String ledger, long startUnixTime, IncludeTransactions includeTransactions) {
+    return getBlocksSync(ledger, startUnixTime, -1, includeTransactions);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的区块</a>
+   * （阻塞）
+   */
+  public GetBlocksResponse getBlocksSync(String ledger, long startUnixTime, long endUnixTime, IncludeTransactions includeTransactions) {
+
+    info(
+        "*** getBlocksSync: ledger={0} startUnixTime={1} endUnixTime={2}",
+        ledger, startUnixTime, endUnixTime);
+
+    try {
+      return queryBlockingStub.getBlocks(blocksRequest(ledger, startUnixTime, endUnixTime, includeTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回账本中的区块数量</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<CountBlocksResponse> countBlocks(String ledger) {
+
+    info("*** blockNumber: ledger={0}", ledger);
+
+    try {
+      return queryFutureStub.countBlocks(blocksRequest(ledger, -1, -1, null));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回账本中的区块数量</a>
+   * （阻塞）
+   */
+  public CountBlocksResponse countBlocksSync(String ledger) {
+
+    info("*** blockNumberSync: ledger={0}", ledger);
+
+    try {
+      return queryBlockingStub.countBlocks(blocksRequest(ledger, -1, -1, null));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private BlocksRequest blocksRequest(String ledger, long startTimestamp, long endTimestamp, IncludeTransactions includeTransactions) {
+
+    BlocksRequest.Builder reqBuilder =
+        BlocksRequest.newBuilder().setLedger(ledger);
+    if (startTimestamp != -1) {
+      reqBuilder.setStartTimestamp(startTimestamp);
+    }
+    if (endTimestamp != -1) {
+      reqBuilder.setEndTimestamp(endTimestamp);
+    }
+    if (includeTransactions == null) {
+      includeTransactions = IncludeTransactions.NONE;
+    }
+    reqBuilder.setIncludeTransactions(includeTransactions);
+
+    return reqBuilder.build();
+  }
+
+  /**
+   * <a
+   * href="#">返回时间戳最新的若干区块</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetBlocksResponse> getRecentBlocks(String ledger, int count, IncludeTransactions includeTransactions) {
+
+    info(
+        "*** getRecentBlocks: ledger={0} count={1} includeTransactions={2}",
+        ledger, count, includeTransactions);
+
+    try {
+      return queryFutureStub.getRecentBlocks(getRecentBlocksRequest(ledger, count, includeTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回时间戳最新的若干区块</a>
+   * （阻塞）
+   */
+  public GetBlocksResponse getRecentBlocksSync(String ledger, int count, IncludeTransactions includeTransactions) {
+
+    info(
+        "*** getRecentBlocksSync: ledger={0} count={1} includeTransactions={2}",
+        ledger, count, includeTransactions);
+
+    try {
+      return queryBlockingStub.getRecentBlocks(getRecentBlocksRequest(ledger, count, includeTransactions));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private RecentBlocksRequest getRecentBlocksRequest(String ledger, int count, IncludeTransactions includeTransactions) {
+
+    RecentBlocksRequest.Builder reqBuilder =
+        RecentBlocksRequest.newBuilder()
+            .setLedger(ledger)
+            .setCount(count);
+    if (includeTransactions == null) {
+      includeTransactions = IncludeTransactions.NONE;
+    }
+    reqBuilder.setIncludeTransactions(includeTransactions);
+
+    return reqBuilder.build();
+  }
+
+  /**
+   * <a
+   * href="#">返回哈希所指定的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionByHashResponse> getTransactionByHash(String ledger, String hash) {
+
+    info("*** getTransactionByHash: ledger={0} hash={1}", ledger, hash);
+
+    try {
+      return queryFutureStub.getTransactionByHash(getTransactionByHashRequest(ledger, hash));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回哈希所指定的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionByHashResponse getTransactionByHashSync(String ledger, String hash) {
+
+    info("*** getTransactionByHashSync: ledger={0} hash={1}", ledger, hash);
+
+    try {
+      return queryBlockingStub.getTransactionByHash(getTransactionByHashRequest(ledger, hash));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private GetTransactionByHashRequest getTransactionByHashRequest(String ledger, String hash) {
+
+    GetTransactionByHashRequest.Builder reqBuilder =
+        GetTransactionByHashRequest.newBuilder().setLedger(ledger);
+    if (hash != null) {
+      reqBuilder.setHash(ByteString.copyFrom(Utils.hexStringToByteArray(hash)));
+    }
+
+    return reqBuilder.build();
+  }
+
+  /**
+   * <a
+   * href="#">返回区块的哈希与事务的index所指定的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionByBlockHashAndIndexResponse> getTransactionByBlockHashAndIndex(
+      String ledger, String blockHash, int index) {
+
+    info(
+        "*** getTransactionByBlockHashAndIndex: ledger={0} blockHash={1} index={2}",
+        ledger, blockHash, index);
+
+    try {
+      return queryFutureStub.getTransactionByBlockHashAndIndex(
+          getTransactionByBlockHashAndIndexRequest(ledger, blockHash, index));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回区块的哈希与事务的index所指定的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionByBlockHashAndIndexResponse getTransactionByBlockHashAndIndexSync(
+      String ledger, String blockHash, int index) {
+
+    info(
+        "*** getTransactionByBlockHashAndIndexSync: ledger={0} blockHash={1} index={2}",
+        ledger, blockHash, index);
+
+    try {
+      return queryBlockingStub.getTransactionByBlockHashAndIndex(
+          getTransactionByBlockHashAndIndexRequest(ledger, blockHash, index));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private GetTransactionByBlockHashAndIndexRequest getTransactionByBlockHashAndIndexRequest(
+      String ledger, String blockHash, int index) {
+
+    GetTransactionByBlockHashAndIndexRequest.Builder reqBuilder =
+        GetTransactionByBlockHashAndIndexRequest.newBuilder().setLedger(ledger).setIndex(index);
+
+    if (blockHash != null) {
+      reqBuilder.setBlockHash(ByteString.copyFrom(Utils.hexStringToByteArray(blockHash)));
+    }
+
+    return reqBuilder.build();
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionsResponse> getTransactions(String ledger, ZonedDateTime startDateTime) {
+    return getTransactions(ledger, startDateTime.toEpochSecond());
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionsResponse> getTransactions(String ledger, ZonedDateTime startDateTime, ZonedDateTime endDateTime) {
+    return getTransactions(ledger, startDateTime.toEpochSecond(), endDateTime.toEpochSecond());
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionsResponse getTransactionsSync(String ledger, ZonedDateTime startDateTime) {
+    return getTransactionsSync(ledger, startDateTime.toEpochSecond());
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionsResponse getTransactionsSync(String ledger, ZonedDateTime startDateTime, ZonedDateTime endDateTime) {
+    return getTransactionsSync(ledger, startDateTime.toEpochSecond(), endDateTime.toEpochSecond());
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionsResponse> getTransactions(String ledger, long startUnixTime) {
+    return getTransactions(ledger, startUnixTime, -1);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<GetTransactionsResponse> getTransactions(String ledger, long startUnixTime, long endUnixTime) {
+
+    info(
+        "*** getTransactions: ledger={0} startUnixTime={1} endUnixTime={2}",
+        ledger, startUnixTime, endUnixTime);
+
+    try {
+      return queryFutureStub.getTransactions(transactionsRequest(ledger, startUnixTime, endUnixTime));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionsResponse getTransactionsSync(String ledger, long startUnixTime) {
+    return getTransactionsSync(ledger, startUnixTime, -1);
+  }
+
+  /**
+   * <a
+   * href="#">返回时间范围内的事务</a>
+   * （阻塞）
+   */
+  public GetTransactionsResponse getTransactionsSync(String ledger, long startUnixTime, long endUnixTime) {
+
+    info(
+        "*** getTransactionsSync: ledger={0} startUnixTime={1} endUnixTime={2}",
+        ledger, startUnixTime, endUnixTime);
+
+    try {
+      return queryBlockingStub.getTransactions(transactionsRequest(ledger, startUnixTime, endUnixTime));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回账本中的事务数量</a>
+   * （非阻塞）
+   */
+  public ListenableFuture<CountTransactionsResponse> countTransactions(String ledger) {
+
+    info("*** blockNumber: ledger={0}", ledger);
+
+    try {
+      return queryFutureStub.countTransactions(transactionsRequest(ledger, -1, -1));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      return null;
+    }
+  }
+
+  /**
+   * <a
+   * href="#">返回账本中的事务数量</a>
+   * （阻塞）
+   */
+  public CountTransactionsResponse countTransactionsSync(String ledger) {
+
+    info("*** blockNumberSync: ledger={0}", ledger);
+
+    try {
+      return queryBlockingStub.countTransactions(transactionsRequest(ledger, -1, -1));
+    } catch (StatusRuntimeException e) {
+      warning("RPC failed: {0}", e.getStatus());
+      throw e;
+    }
+  }
+
+  private TransactionsRequest transactionsRequest(String ledger, long startTimestamp, long endTimestamp) {
+
+    TransactionsRequest.Builder reqBuilder =
+        TransactionsRequest.newBuilder().setLedger(ledger);
+    if (startTimestamp != -1) {
+      reqBuilder.setStartTimestamp(startTimestamp);
+    }
+    if (endTimestamp != -1) {
+      reqBuilder.setEndTimestamp(endTimestamp);
+    }
+
+    return reqBuilder.build();
+  }
+
+  private void info(String msg, Object... params) {
+    logger.log(Level.INFO, msg, params);
+  }
+
+  private void warning(String msg, Object... params) {
+    logger.log(Level.WARNING, msg, params);
+  }
+}
diff --git a/src/main/java/org/bdware/bdledger/api/grpc/GrpcHeaderInterceptor.java b/src/main/java/org/bdware/bdledger/api/grpc/GrpcHeaderInterceptor.java
new file mode 100644
index 0000000..0543470
--- /dev/null
+++ b/src/main/java/org/bdware/bdledger/api/grpc/GrpcHeaderInterceptor.java
@@ -0,0 +1,33 @@
+package org.bdware.bdledger.api.grpc;
+
+import io.grpc.*;
+import io.grpc.stub.AbstractStub;
+import org.bdware.bdledger.api.grpc.pb.NodeGrpc;
+
+public class GrpcHeaderInterceptor implements ClientInterceptor {
+
+    private final Metadata extraHeaders;
+
+    public GrpcHeaderInterceptor(Metadata metadata) {
+        this.extraHeaders = metadata;
+    }
+
+    @Override
+    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
+        return new ForwardingClientCall.SimpleForwardingClientCall<ReqT,RespT>(next.newCall(method, callOptions)) {
+            @Override
+            public void start(Listener<RespT> responseListener, Metadata headers) {
+                // 合并额外的头信息
+                headers.merge(extraHeaders);
+                super.start(responseListener, headers);
+            }
+        };
+    }
+
+    public static <T extends AbstractStub<T>> T attachHeaders(T stub, Metadata metadata) {
+        Channel channel = stub.getChannel();
+        Channel interceptedChannel = ClientInterceptors.intercept(channel, new GrpcHeaderInterceptor(metadata));
+        return stub.withChannel(interceptedChannel);
+    }
+
+}
diff --git a/src/main/java/org/bdware/bdledger/api/grpc/Utils.java b/src/main/java/org/bdware/bdledger/api/grpc/Utils.java
new file mode 100644
index 0000000..04cd518
--- /dev/null
+++ b/src/main/java/org/bdware/bdledger/api/grpc/Utils.java
@@ -0,0 +1,26 @@
+package org.bdware.bdledger.api.grpc;
+
+public class Utils {
+
+  public static byte[] hexStringToByteArray(String s) {
+    if (s.startsWith("0x")) {
+      s = s.substring(2);
+    }
+    int l = s.length();
+    byte[] data = new byte[l / 2];
+    for (int i = 0; i < l; i += 2) {
+      data[i / 2] =
+          (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
+    }
+    return data;
+  }
+
+  public static String byteArrayToHexString(byte[] bs) {
+    StringBuilder data = new StringBuilder();
+    for (byte b : bs) {
+      data.append(Integer.toHexString((b >> 4) & 0xf));
+      data.append(Integer.toHexString(b & 0xf));
+    }
+    return data.toString();
+  }
+}