Blockchain as a Service:Java SDK usage example

What the sample demonstrates

When the program runs successfully, it performs these operations in order:

1. Enroll user — authenticates with the network using userName and secret.

2. Connect to the channel — reads connection-profile-standard.yaml, connects to the channel's peer nodes, and starts listening for block events.

3. Read block information — retrieves block data from the ledger and prints it to the console.

4. Invoke the sacc chaincode — writes a new ledger entry and reads it back.

5. Disconnect — closes the connection to the peer.

Prerequisites

Before you begin, ensure that you have:

• A BaaS network with at least one channel created

• A user account and password for that network

• Java 1.8 runtime environment and Apache Maven installed

• The connection-profile-standard.yaml SDK configuration file downloaded from the BaaS console

Verify your Java and Maven installation:

mvn -version

The output should show Apache Maven 3.5.3 and Java version 1.8.x:

Apache Maven 3.5.3 (3383c37e1f9e9b3bc3df5050c29c8aff9f295297; 2018-02-25T03:49:05+08:00)
...
Java version: 1.8.0_161, vendor: Oracle Corporation

Step 1: Download the sample program

Download java-sdk-demo-1.4.5 and extract it. Copy the SDK configuration file connection-profile-standard.yaml into the extracted java-sdk-demo directory.

After extraction and copying, the directory structure looks like this:

java-sdk-demo-1.4.5/
├── chaincode/
│   └── sacc.out
├── lib/
│   ├── fabric-sdk-java-1.4.5-jar-with-dependencies.jar
│   └── fabric-sdk-java-1.4.5-sources.jar
├── src/
│   └── main/java/com/aliyun/baas/
│       └── Main.java
└── connection-profile-standard.yaml   (copied from BaaS console)

Step 2: Install dependencies

The sample ships with the Fabric Java SDK JAR files under ./lib/. From inside the java-sdk-demo-1.4.5 directory, run both Maven install commands to register them in your local Maven repository:

mvn install:install-file \
  -Dfile=./lib/fabric-sdk-java-1.4.5-jar-with-dependencies.jar \
  -DgroupId=org.hyperledger.fabric-sdk-java \
  -DartifactId=fabric-sdk-java \
  -Dversion=1.4.5 \
  -Dpackaging=jar

mvn install:install-file \
  -Dfile=./lib/fabric-sdk-java-1.4.5-sources.jar \
  -DgroupId=org.hyperledger.fabric-sdk-java \
  -DartifactId=fabric-sdk-java \
  -Dversion=1.4.5 \
  -Dpackaging=jar \
  -Dclassifier=sources

Step 3: Deploy the chaincode

Upload chaincode/sacc.out to BaaS and instantiate it. For instructions, see Deploy Chaincode.

Step 4: Configure and run the sample

1. Open the java-sdk-demo project in a Java IDE (IntelliJ IDEA, for example).

2. Open src/main/java/com/aliyun/baas/Main.java and set the following variables:

   Variable	Description	Where to find it	Example
   channelName	The name of the channel to connect to	BaaS console > Channels	"first-channel"
   userName	Your BaaS user account name	BaaS console > Users	—
   secret	Your BaaS user password. If you forgot the password, reset it from the BaaS console before proceeding.	BaaS console > Users	—
   chaincodeName	The name of the instantiated chaincode	sacc when using sacc.out	"sacc"
   chaincodeVersion	The version of the instantiated chaincode	1.0.0 when using sacc.out	"1.0.0"

3. Run com.aliyun.baas.Main as the main class.

What's next

For the full Fabric Java SDK API reference and advanced usage, see the fabric-sdk-java repository.