BAEL-3091: The Prototype Pattern in Java (changed code based on valid comments from a reader)

ethereum/src/main/java/com/baeldung/ethereumj/ApplicationMain.java

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+package com.baeldung.ethereumj;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
+import org.springframework.boot.web.support.SpringBootServletInitializer;
+
+@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
+@SpringBootApplication
+public class ApplicationMain extends SpringBootServletInitializer {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ApplicationMain.class, args);
+    }
+}

ethereum/src/main/java/com/baeldung/ethereumj/Constants.java

@@ -0,0 +1,9 @@
+package com.baeldung.ethereumj;
+
+public class Constants {
+
+    public static final String ENDPOINT_ONE = "/api/get/bestblock/";
+    public static final String ENDPOINT_TWO = "/api/get/difficulty/";
+    public static final String RESPONSE_TYPE ="application/json/";
+
+}

ethereum/src/main/java/com/baeldung/ethereumj/beans/EthBean.java

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+package com.baeldung.ethereumj.beans;
+
+import com.baeldung.ethereumj.listeners.EthListener;
+import org.ethereum.core.Block;
+import org.ethereum.facade.Ethereum;
+import org.ethereum.facade.EthereumFactory;
+
+import java.math.BigInteger;
+
+public class EthBean {
+    private Ethereum ethereum;
+
+    public void start() {
+        this.ethereum = EthereumFactory.createEthereum();
+        this.ethereum.addListener(new EthListener(ethereum));
+    }
+
+    public Block getBestBlock() {
+        return this.ethereum.getBlockchain().getBestBlock();
+    }
+
+    public BigInteger getTotalDifficulty() {
+        return this.ethereum.getBlockchain().getTotalDifficulty();
+    }
+}

ethereum/src/main/java/com/baeldung/ethereumj/config/EthConfig.java

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+package com.baeldung.ethereumj.config;
+
+import com.baeldung.ethereumj.beans.EthBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import java.util.concurrent.Executors;
+
+@Configuration
+public class EthConfig {
+
+    @Bean
+    EthBean ethBeanConfig() throws Exception {
+        EthBean eBean = new EthBean();
+        Executors.newSingleThreadExecutor().submit(eBean::start);
+        return eBean;
+    }
+}

ethereum/src/main/java/com/baeldung/ethereumj/controllers/EthController.java

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+package com.baeldung.ethereumj.controllers;
+
+import com.baeldung.ethereumj.Constants;
+import com.baeldung.ethereumj.beans.EthBean;
+import com.baeldung.ethereumj.transfer.EthResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import javax.annotation.PostConstruct;
+import javax.servlet.ServletContext;
+
+@RestController
+public class EthController {
+
+    @Autowired
+    EthBean ethBean;
+    @Autowired
+    private ServletContext servletContext;
+    private Logger l = LoggerFactory.getLogger(EthController.class);
+
+    @RequestMapping(Constants.ENDPOINT_ONE)
+    public EthResponse getBestBlock() {
+        l.debug("Request received - fetching best block.");
+        EthResponse r = new EthResponse();
+        r.setResponse(ethBean.getBestBlock().toString());
+        return r;
+    }
+
+    @RequestMapping(Constants.ENDPOINT_TWO)
+    public EthResponse getTotalDifficulty() {
+        l.debug("Request received - calculating total difficulty.");
+        EthResponse r = new EthResponse();
+        r.setResponse(ethBean.getTotalDifficulty().toString());
+        return r;
+    }
+
+    @PostConstruct
+    public void showIt() {
+        l.debug(servletContext.getContextPath());
+    }
+}

ethereum/src/main/java/com/baeldung/ethereumj/listeners/EthListener.java

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+package com.baeldung.ethereumj.listeners;
+
+import org.ethereum.core.Block;
+import org.ethereum.core.TransactionReceipt;
+import org.ethereum.facade.Ethereum;
+import org.ethereum.listener.EthereumListenerAdapter;
+import org.ethereum.util.BIUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.math.BigInteger;
+import java.util.List;
+
+public class EthListener extends EthereumListenerAdapter {
+
+    private Logger l = LoggerFactory.getLogger(EthListener.class);
+    private Ethereum ethereum;
+    private boolean syncDone = false;
+    private static final int thou = 1000;
+
+    private void out(String t) {
+        l.info(t);
+    }
+
+    private String calcNetHashRate(Block block) {
+        String response = "Net hash rate not available";
+        if (block.getNumber() > thou) {
+            long timeDelta = 0;
+            for (int i = 0; i < thou; ++i) {
+                Block parent = ethereum
+                  .getBlockchain()
+                  .getBlockByHash(block.getParentHash());
+                timeDelta += Math.abs(block.getTimestamp() - parent.getTimestamp());
+            }
+            response = String.valueOf(block
+              .getDifficultyBI()
+              .divide(BIUtil.toBI(timeDelta / thou))
+              .divide(new BigInteger("1000000000"))
+              .doubleValue()) + " GH/s";
+        }
+        return response;
+    }
+
+    public EthListener(Ethereum ethereum) {
+        this.ethereum = ethereum;
+    }
+
+    @Override
+    public void onBlock(Block block, List<TransactionReceipt> receipts) {
+        if (syncDone) {
+            out("Net hash rate: " + calcNetHashRate(block));
+            out("Block difficulty: " + block.getDifficultyBI().toString());
+            out("Block transactions: " + block.getTransactionsList().toString());
+            out("Best block (last block): " + ethereum
+              .getBlockchain()
+              .getBestBlock().toString());
+            out("Total difficulty: " + ethereum
+              .getBlockchain()
+              .getTotalDifficulty().toString());
+        }
+    }
+
+    @Override
+    public void onSyncDone(SyncState state) {
+        out("onSyncDone " + state);
+        if (!syncDone) {
+            out(" ** SYNC DONE ** ");
+            syncDone = true;
+        }
+    }
+}

ethereum/src/main/java/com/baeldung/ethereumj/transfer/EthResponse.java

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+package com.baeldung.ethereumj.transfer;
+
+public class EthResponse {
+
+    private String response;
+
+    public String getResponse() {
+        return response;
+    }
+
+    public void setResponse(String response) {
+        this.response = response;
+    }
+}

ethereum/src/main/java/com/baeldung/web3j/Template.java

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+package com.baeldung.web3j;
+
+import com.baeldung.web3j.contracts.Greeting;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.web3j.crypto.Credentials;
+import org.web3j.crypto.WalletUtils;
+import org.web3j.protocol.Web3j;
+import org.web3j.protocol.core.methods.response.TransactionReceipt;
+import org.web3j.protocol.http.HttpService;
+import org.web3j.tx.Contract;
+import org.web3j.tx.ManagedTransaction;
+
+public class Template {
+
+    private Logger l = LoggerFactory.getLogger(Template.class);
+
+    private void deployContract() throws Exception{
+
+        Web3j web3j = Web3j.build(new HttpService("https://rinkeby.infura.io/<your_token>"));
+
+        Credentials credentials =
+            WalletUtils.loadCredentials(
+               "<password>",
+               "/path/to/<walletfile>");
+
+        Greeting contract = Greeting.deploy(
+            web3j, credentials,
+            ManagedTransaction.GAS_PRICE, Contract.GAS_LIMIT,
+            "Hello blockchain world!").send();
+
+        String contractAddress = contract.getContractAddress();
+        l.debug("Smart contract deployed to address "+ contractAddress);
+
+        l.debug("Value stored in remote smart contract: "+ contract.greet().send());
+
+        TransactionReceipt transactionReceipt = contract.setGreeting("Well hello again").send();
+
+        l.debug("New value stored in remote smart contract: "+ contract.greet().send());
+    }
+}

ethereum/src/main/java/com/baeldung/web3j/config/AppConfig.java

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+package com.baeldung.web3j.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableAsync;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
+import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+import org.springframework.web.servlet.resource.PathResourceResolver;
+import org.springframework.web.servlet.view.JstlView;
+import org.springframework.web.servlet.view.UrlBasedViewResolver;
+
+import java.util.concurrent.Executor;
+
+@Configuration
+@EnableWebMvc
+@EnableAsync
+@ComponentScan("com.baeldung.web3j")
+public class AppConfig implements WebMvcConfigurer {
+
+    public void addViewControllers(ViewControllerRegistry registry) {
+        registry.addViewController("/").setViewName("index");
+    }
+
+    /**
+     * Static resource locations including themes
+     */
+    @Override
+    public void addResourceHandlers(ResourceHandlerRegistry registry) {
+        registry.addResourceHandler("/resources/**/*")
+                .addResourceLocations("/", "/resources/")
+                .setCachePeriod(3600)
+                .resourceChain(true)
+                .addResolver(new PathResourceResolver());
+    }
+
+    /**
+     * View resolver for JSP
+     */
+    @Bean
+    public UrlBasedViewResolver viewResolver() {
+        UrlBasedViewResolver resolver = new UrlBasedViewResolver();
+        resolver.setPrefix("/WEB-INF/jsp/");
+        resolver.setSuffix(".jsp");
+        resolver.setViewClass(JstlView.class);
+        return resolver;
+    }
+
+    /**
+     * Configuration for async thread bean
+     *
+     * More: https://docs.spring.io/autorepo/docs/spring-framework/5.0.3.RELEASE/javadoc-api/org/springframework/scheduling/SchedulingTaskExecutor.html
+     */
+    @Bean
+    public Executor asyncExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(2);
+        executor.setMaxPoolSize(2);
+        executor.setQueueCapacity(500);
+        executor.setThreadNamePrefix("CsvThread");
+        executor.initialize();
+        return executor;
+    }
+
+}

ethereum/src/main/java/com/baeldung/web3j/config/WebAppInitializer.java

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+package com.baeldung.web3j.config;
+
+import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
+
+public class WebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
+
+    //AbstractDispatcherServletInitializer override DEFAULT_SERVLET_NAME
+    @Override
+    protected String getServletName() {
+        return "dispatcher";
+    }
+
+    @Override
+    protected Class<?>[] getRootConfigClasses() {
+        return new Class[]{};
+    }
+
+    @Override
+    protected Class<?>[] getServletConfigClasses() {
+        return new Class[]{AppConfig.class};
+    }
+
+    @Override
+    protected String[] getServletMappings() {
+        return new String[]{"/"};
+    }
+
+}

ethereum/src/main/java/com/baeldung/web3j/constants/Constants.java

@@ -0,0 +1,18 @@
+package com.baeldung.web3j.constants;
+
+public class Constants {
+
+    public static final String API_BLOCK = "/api/block";
+    public static final String API_ACCOUNTS = "/api/accounts";
+    public static final String API_TRANSACTIONS = "/api/transactions";
+    public static final String API_BALANCE = "/api/balance";
+
+    public static final String GENERIC_EXCEPTION = "Exception encountered!";
+    public static final String PLEASE_SUPPLY_REAL_DATA = "Please Supply Real Data!";
+
+    public static final String DEFAULT_ADDRESS = "0x281055afc982d96fab65b3a49cac8b878184cb16";
+    public static final String DEFAULT_CONTRACT_ADDRESS = "00000000000000000000";
+
+
+
+}

ethereum/src/main/java/com/baeldung/web3j/contracts/Example.java

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+package com.baeldung.web3j.contracts;
+
+import java.math.BigInteger;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import org.web3j.abi.TypeReference;
+import org.web3j.abi.datatypes.Function;
+import org.web3j.abi.datatypes.Type;
+import org.web3j.crypto.Credentials;
+import org.web3j.protocol.Web3j;
+import org.web3j.protocol.core.RemoteCall;
+import org.web3j.protocol.core.methods.response.TransactionReceipt;
+import org.web3j.tx.Contract;
+import org.web3j.tx.TransactionManager;
+
+/**
+ * <p>Auto generated code.
+ * <p><strong>Do not modify!</strong>
+ * <p>Please use the <a href="https://docs.web3j.io/command_line.html">web3j command line tools</a>,
+ * or the org.web3j.codegen.SolidityFunctionWrapperGenerator in the 
+ * <a href="https://github.com/web3j/web3j/tree/master/codegen">codegen module</a> to update.
+ *
+ * <p>Generated with web3j version 3.3.1.
+ */
+public class Example extends Contract {
+    private static final String BINARY = "0x60606040523415600e57600080fd5b60848061001c6000396000f300606060405260043610603f576000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063b818dacd146044575b600080fd5b3415604e57600080fd5b60546056565b005b5600a165627a7a72305820bebcbbdf06550591bc772dfcb0eadc842f95953869feb7a9528bac91487d95240029";
+
+    protected static final HashMap<String, String> _addresses;
+
+    static {
+        _addresses = new HashMap<>();
+    }
+
+    protected Example(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
+        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
+    }
+
+    protected Example(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
+        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
+    }
+
+    public static RemoteCall<Example> deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
+        return deployRemoteCall(Example.class, web3j, credentials, gasPrice, gasLimit, BINARY, "");
+    }
+
+    public static RemoteCall<Example> deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
+        return deployRemoteCall(Example.class, web3j, transactionManager, gasPrice, gasLimit, BINARY, "");
+    }
+
+    public RemoteCall<TransactionReceipt> ExampleFunction() {
+        final Function function = new Function(
+                "ExampleFunction", 
+                Arrays.<Type>asList(), 
+                Collections.<TypeReference<?>>emptyList());
+        return executeRemoteCallTransaction(function);
+    }
+
+    public static Example load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
+        return new Example(contractAddress, web3j, credentials, gasPrice, gasLimit);
+    }
+
+    public static Example load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
+        return new Example(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
+    }
+
+    protected String getStaticDeployedAddress(String networkId) {
+        return _addresses.get(networkId);
+    }
+
+    public static String getPreviouslyDeployedAddress(String networkId) {
+        return _addresses.get(networkId);
+    }
+}

ethereum/src/main/java/com/baeldung/web3j/contracts/Greeting.java

@@ -0,0 +1,71 @@
+package com.baeldung.web3j.contracts;
+
+import java.math.BigInteger;
+import java.util.Arrays;
+import java.util.Collections;
+import org.web3j.abi.FunctionEncoder;
+import org.web3j.abi.TypeReference;
+import org.web3j.abi.datatypes.Function;
+import org.web3j.abi.datatypes.Type;
+import org.web3j.abi.datatypes.Utf8String;
+import org.web3j.crypto.Credentials;
+import org.web3j.protocol.Web3j;
+import org.web3j.protocol.core.RemoteCall;
+import org.web3j.protocol.core.methods.response.TransactionReceipt;
+import org.web3j.tx.Contract;
+import org.web3j.tx.TransactionManager;
+
+/**
+ * <p>Auto generated code.
+ * <p><strong>Do not modify!</strong>
+ * <p>Please use the <a href="https://docs.web3j.io/command_line.html">web3j command line tools</a>,
+ * or the org.web3j.codegen.SolidityFunctionWrapperGenerator in the
+ * <a href="https://github.com/web3j/web3j/tree/master/codegen">codegen module</a> to update.
+ *
+ * <p>Generated with web3j version 3.3.1.
+ */
+public class Greeting extends Contract {
+    private static final String BINARY = "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";
+
+    protected Greeting(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
+        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
+    }
+
+    protected Greeting(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
+        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
+    }
+
+    public RemoteCall<TransactionReceipt> setGreeting(String _message) {
+        final Function function = new Function(
+                "setGreeting",
+                Arrays.<Type>asList(new org.web3j.abi.datatypes.Utf8String(_message)),
+                Collections.<TypeReference<?>>emptyList());
+        return executeRemoteCallTransaction(function);
+    }
+
+    public RemoteCall<String> greet() {
+        final Function function = new Function("greet",
+                Arrays.<Type>asList(),
+                Arrays.<TypeReference<?>>asList(new TypeReference<Utf8String>() {}));
+        return executeRemoteCallSingleValueReturn(function, String.class);
+    }
+
+    public static RemoteCall<Greeting> deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit, String _message) {
+        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(new org.web3j.abi.datatypes.Utf8String(_message)));
+        return deployRemoteCall(Greeting.class, web3j, credentials, gasPrice, gasLimit, BINARY, encodedConstructor);
+    }
+
+    public static RemoteCall<Greeting> deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit, String _message) {
+        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(new org.web3j.abi.datatypes.Utf8String(_message)));
+        return deployRemoteCall(Greeting.class, web3j, transactionManager, gasPrice, gasLimit, BINARY, encodedConstructor);
+    }
+
+    public static Greeting load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
+        return new Greeting(contractAddress, web3j, credentials, gasPrice, gasLimit);
+    }
+
+    public static Greeting load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
+        return new Greeting(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
+    }
+}
+

ethereum/src/main/java/com/baeldung/web3j/controllers/EthereumRestController.java

@@ -0,0 +1,103 @@
+package com.baeldung.web3j.controllers;
+
+import com.baeldung.web3j.constants.Constants;
+import com.baeldung.web3j.helpers.TimeHelper;
+import com.baeldung.web3j.services.Web3Service;
+import com.baeldung.web3j.transfers.ResponseTransfer;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.bind.annotation.RestController;
+import org.web3j.protocol.core.methods.response.EthAccounts;
+import org.web3j.protocol.core.methods.response.EthBlockNumber;
+import org.web3j.protocol.core.methods.response.EthGetBalance;
+import org.web3j.protocol.core.methods.response.EthGetTransactionCount;
+
+import java.time.Instant;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+
+import static com.baeldung.web3j.constants.Constants.GENERIC_EXCEPTION;
+
+@RestController
+public class EthereumRestController {
+
+    @Autowired
+    Web3Service web3Service;
+
+    @RequestMapping(value = Constants.API_BLOCK, method = RequestMethod.GET)
+    public Future<ResponseTransfer> getBlock() {
+        ResponseTransfer responseTransfer = new ResponseTransfer();
+        Instant start = TimeHelper.start();
+
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                EthBlockNumber result = web3Service.getBlockNumber();
+                responseTransfer.setMessage(result.toString());
+            } catch (Exception e) {
+                responseTransfer.setMessage(GENERIC_EXCEPTION);
+            }
+            return responseTransfer;
+        }).thenApplyAsync(result -> {
+            result.setPerformance(TimeHelper.stop(start));
+            return result;
+        });
+    }
+
+    @RequestMapping(value = Constants.API_ACCOUNTS, method = RequestMethod.GET)
+    public Future<ResponseTransfer> getAccounts() {
+        ResponseTransfer responseTransfer = new ResponseTransfer();
+        Instant start = TimeHelper.start();
+
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                EthAccounts result = web3Service.getEthAccounts();
+                responseTransfer.setMessage(result.toString());
+            } catch (Exception e) {
+                responseTransfer.setMessage(GENERIC_EXCEPTION);
+            }
+            return responseTransfer;
+
+        }).thenApplyAsync(result -> {
+            result.setPerformance(TimeHelper.stop(start));
+            return result;
+        });
+    }
+
+    @RequestMapping(value = Constants.API_TRANSACTIONS, method = RequestMethod.GET)
+    public Future<ResponseTransfer> getTransactions() {
+        ResponseTransfer responseTransfer = new ResponseTransfer();
+        Instant start = TimeHelper.start();
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                EthGetTransactionCount result = web3Service.getTransactionCount();
+                responseTransfer.setMessage(result.toString());
+            } catch (Exception e) {
+                responseTransfer.setMessage(GENERIC_EXCEPTION);
+            }
+            return responseTransfer;
+        }).thenApplyAsync(result -> {
+            result.setPerformance(TimeHelper.stop(start));
+            return result;
+        });
+    }
+
+    @RequestMapping(value = Constants.API_BALANCE, method = RequestMethod.GET)
+    public Future<ResponseTransfer> getBalance() {
+        ResponseTransfer responseTransfer = new ResponseTransfer();
+        Instant start = TimeHelper.start();
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                EthGetBalance result = web3Service.getEthBalance();
+                responseTransfer.setMessage(result.toString());
+            } catch (Exception e) {
+                responseTransfer.setMessage(GENERIC_EXCEPTION);
+            }
+            return responseTransfer;
+        }).thenApplyAsync(result -> {
+            result.setPerformance(TimeHelper.stop(start));
+            return result;
+        });
+    }
+
+}

ethereum/src/main/java/com/baeldung/web3j/helpers/TimeHelper.java

@@ -0,0 +1,16 @@
+package com.baeldung.web3j.helpers;
+
+import java.time.Duration;
+import java.time.Instant;
+
+public class TimeHelper {
+
+    public static Instant start() {
+        return Instant.now();
+    }
+
+    public static Duration stop(Instant start) {
+        Instant end = Instant.now();
+        return Duration.between(start, end);
+    }
+}

ethereum/src/main/java/com/baeldung/web3j/services/Web3Service.java

@@ -0,0 +1,151 @@
+package com.baeldung.web3j.services;
+
+import com.baeldung.web3j.contracts.Example;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.web3j.abi.FunctionEncoder;
+import org.web3j.abi.datatypes.Function;
+import org.web3j.crypto.Credentials;
+import org.web3j.crypto.WalletUtils;
+import org.web3j.protocol.Web3j;
+import org.web3j.protocol.core.DefaultBlockParameter;
+import org.web3j.protocol.core.methods.request.Transaction;
+import org.web3j.protocol.core.methods.response.EthAccounts;
+import org.web3j.protocol.core.methods.response.EthBlockNumber;
+import org.web3j.protocol.core.methods.response.EthGetBalance;
+import org.web3j.protocol.core.methods.response.EthGetTransactionCount;
+import org.web3j.protocol.http.HttpService;
+import org.web3j.tx.Contract;
+import org.web3j.tx.ManagedTransaction;
+
+import java.io.File;
+import java.math.BigInteger;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+import static com.baeldung.web3j.constants.Constants.DEFAULT_ADDRESS;
+import static com.baeldung.web3j.constants.Constants.GENERIC_EXCEPTION;
+import static com.baeldung.web3j.constants.Constants.PLEASE_SUPPLY_REAL_DATA;
+
+@Service
+public class Web3Service {
+
+    private Web3j web3j = Web3j.build(new HttpService());
+
+    //Create and Init the default Web3J connection
+    public void customInit(String provider) {
+        this.web3j = Web3j.build(new HttpService(provider));
+    }
+
+    //Convert to and from supplied contract ABI bytecode
+    public static String toBinary(String bytecode) {
+        return bytecode.replaceFirst("^0x", "");
+    }
+
+    public static String toByteCode(String binary) {
+        return "0x" + binary;
+    }
+
+    public EthBlockNumber getBlockNumber() {
+        EthBlockNumber result = new EthBlockNumber();
+        try {
+            result = this.web3j.ethBlockNumber().sendAsync().get();
+        } catch (Exception ex) {
+            System.out.println(GENERIC_EXCEPTION);
+        }
+        return result;
+    }
+
+    public EthAccounts getEthAccounts() {
+        EthAccounts result = new EthAccounts();
+        try {
+             result = this.web3j.ethAccounts().sendAsync().get();
+        } catch (Exception ex) {
+            System.out.println(GENERIC_EXCEPTION);
+        }
+        return result;
+    }
+
+    public EthGetTransactionCount getTransactionCount() {
+        EthGetTransactionCount result = new EthGetTransactionCount();
+        try {
+             result = this.web3j.ethGetTransactionCount(DEFAULT_ADDRESS, DefaultBlockParameter.valueOf("latest")).sendAsync().get();
+        } catch (Exception ex) {
+            System.out.println(GENERIC_EXCEPTION);
+        }
+        return result;
+    }
+
+    public EthGetBalance getEthBalance() {
+        EthGetBalance result = new EthGetBalance();
+        try {
+            result = this.web3j.ethGetBalance(DEFAULT_ADDRESS, DefaultBlockParameter.valueOf("latest")).sendAsync().get();
+        } catch (Exception ex) {
+            System.out.println(GENERIC_EXCEPTION);
+        }
+        return result;
+    }
+
+    public String fromScratchContractExample() {
+
+        String contractAddress = "";
+
+        try {
+            //Create a wallet
+            WalletUtils.generateNewWalletFile("PASSWORD", new File("/path/to/destination"), true);
+            //Load the credentials from it
+            Credentials credentials = WalletUtils.loadCredentials("PASSWORD", "/path/to/walletfile");
+
+            //Deploy contract to address specified by wallet
+            Example contract = Example.deploy(this.web3j,
+                    credentials,
+                    ManagedTransaction.GAS_PRICE,
+                    Contract.GAS_LIMIT).send();
+
+            //Het the address
+            contractAddress = contract.getContractAddress();
+
+        } catch (Exception ex) {
+            System.out.println(PLEASE_SUPPLY_REAL_DATA);
+            return PLEASE_SUPPLY_REAL_DATA;
+        }
+        return contractAddress;
+    }
+
+    @Async
+    public String sendTx() {
+        String transactionHash = "";
+
+        try {
+            List inputParams = new ArrayList();
+            List outputParams = new ArrayList();
+            Function function = new Function("fuctionName", inputParams, outputParams);
+
+            String encodedFunction = FunctionEncoder.encode(function);
+
+            BigInteger nonce = BigInteger.valueOf(100);
+            BigInteger gasprice = BigInteger.valueOf(100);
+            BigInteger gaslimit = BigInteger.valueOf(100);
+
+            Transaction transaction = Transaction.createFunctionCallTransaction("FROM_ADDRESS", nonce, gasprice, gaslimit, "TO_ADDRESS", encodedFunction);
+
+            org.web3j.protocol.core.methods.response.EthSendTransaction transactionResponse = web3j.ethSendTransaction(transaction).sendAsync().get();
+            transactionHash = transactionResponse.getTransactionHash();
+
+        } catch (Exception ex) {
+            System.out.println(PLEASE_SUPPLY_REAL_DATA);
+            return PLEASE_SUPPLY_REAL_DATA;
+        }
+
+        return transactionHash;
+    }
+}
+
+
+
+
+
+
+
+

ethereum/src/main/java/com/baeldung/web3j/transfers/ResponseTransfer.java

@@ -0,0 +1,28 @@
+package com.baeldung.web3j.transfers;
+
+import java.time.Duration;
+
+public class ResponseTransfer {
+
+    public ResponseTransfer() {}
+
+    private Duration performance;
+    private String message;
+
+    public Duration getPerformance() {
+        return performance;
+    }
+
+    public void setPerformance(Duration performance) {
+        this.performance = performance;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
+
+}