Java SDK Getting Started

Prerequisites

Before you begin, ensure that you have:

• A BaaS node deployed on the BaaS platform

• The node's IP address and port number (available on the node details page)

• IntelliJ IDEA installed

• Maven installed

• Java Development Kit (JDK) installed

Step 1: Prepare your environment

Step 2: Set up the project

1. In IntelliJ IDEA, create a Maven-based demo project. After the project is created, the directory structure looks like this:

   

2. In the java directory, create a package named com.example.demo. Copy the contents of DemoSample.java into this package, and place the four certificate files (client.crt, client.key, trustCa, and user.key) in the resources directory. Download DemoSample.java.

   The demo project requires the EVM bytecode compiled from your Solidity contract source code. For details on writing Solidity contracts, see Solidity contract development. For the compilation tool, see Solidity contract compilation tool.

   

3. Add the BaaS SDK and logging dependencies to pom.xml. Always use the latest SDK version.

   <dependencies>
       <dependency>
           <groupId>com.alipay.mychainx</groupId>
           <artifactId>mychainx-sdk</artifactId>
               <!-- Use the latest SDK version -->
           <version>0.10.2.6</version>
       </dependency>
   
       <dependency>
           <groupId>org.slf4j</groupId>
           <artifactId>slf4j-log4j12</artifactId>
           <version>1.8.0-alpha0</version>
       </dependency>
   </dependencies>
   
   <build>
       <extensions>
           <extension>
               <groupId>kr.motd.maven</groupId>
               <artifactId>os-maven-plugin</artifactId>
               <version>1.6.1</version>
           </extension>
       </extensions>
   </build>

4. Add log4j.properties to the resources directory with the following content:

   log4j.rootLogger=INFO, R
   
   # Console output
   log4j.appender.stdout=org.apache.log4j.ConsoleAppender
   log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
   log4j.appender.stdout.layout.ConversionPattern=[QC] %p [%t] %C.%M(%L) | %m%n
   
   # File output
   log4j.appender.R=org.apache.log4j.DailyRollingFileAppender
   log4j.appender.R.File=./sdk.log
   log4j.appender.R.layout=org.apache.log4j.PatternLayout
   log4j.appender.R.layout.ConversionPattern=%d-[TS] %p %t %c - %m%n
   
   # Disable verbose SDK internal logs
   log4j.logger.MychainClient=OFF

   If you use logback instead of log4j, add this to your logback configuration:

   <logger name="MychainClient" level="OFF"/>

Step 3: Compile the project

In the project root directory, run:

mvn clean compile

Step 4: Run the application

Run the project entry point DemoSample.java. Logs are written to ./sdk.log in the project root directory.

To verify the connection succeeded, check sdk.log for the "Hand shake success" message.

When all operations complete successfully, the console output is:

create testAccount1 success.
create testAccount2 success.
deploy contract success.
issue success.
transfer success.
check account balance success.

Troubleshooting

MychainBaseResult<ReplyTransactionReceipt> result = sdk.getContractService()
    .deployContract(
        DeployContractRequest.build(adminAccount.getIdentity(),
            Utils.getIdentityByName(testContractId, env), contractCode, VMTypeEnum.EVM,
            contractParameters, BigInteger.ZERO, params));
assertTrue(result.isSuccess());
assertEquals(0, result.getData().getTransactionReceipt().getResult());

Example execution flow

The following shows the complete execution sequence in DemoSample.java:

1. Initialize the environment

   // Step 1: Initialize logger
   initLogger();
   
   // Step 2: Initialize the BaaS environment
   env = initMychainEnv();

2. Create a transaction

   // Step 4: Initialize account objects
   initAccount();
   
   // Step 5: Initialize private key list for signing transactions
   initPrivateKeyList();
   
   // Step 6: Create testAccount1 and testAccount2 on-chain
   createAccount();

3. Deploy a smart contract

   // Step 7: Deploy the EVM contract using testAccount1
   deployContract();

4. Purchase points

   // Step 8: Issue 100 credits to testAccount2
   issue();

5. Conduct an account transfer

   // Step 9: Transfer 50 credits from testAccount2 to testAccount1
   transfer();

6. Query and verify the balance

   // Step 10: Query testAccount2's balance (expected: 50)
   BigInteger balance = query(test2PrivateKeyArrayList, testAccount2);
   
   // Step 11: Assert the balance equals 50
   expect(balance, BigInteger.valueOf(50));

7. Disconnect the SDK

   // Step 12: Shut down the SDK connection
   sdk.shutDown();

What's next

• Learn how to write and compile Solidity contracts: Solidity contract development

• Explore the SDK API reference for available operations

• View transaction details on the BaaS platform