BAEL-3446 (#12872)

* BAEL-3446 a simple market data streaming app for the article.

* BAEL-3446 add unit tests for the article code.

* BAEL-3446 increase version, activate module in the parent pom, update readme.

* BAEL-3446 improve the code semantically.

* BAEL-3446 remove unnecessary files

* BAEL-3446 fix continuation indentation as 2

* BAEL-3446 put new module in the correct profile

Co-authored-by: Yavuz Tas <ytas@vwd.com>

libraries-7/README.md

@@ -0,0 +1,11 @@
+## Libraries-7
+
+This module contains articles about various Java libraries. 
+These are small libraries that are relatively easy to use and do not require any separate module of their own.
+
+The code examples related to different libraries are each in their own module.
+
+Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-modules) we already have separate modules. Please make sure to have a look at the existing modules in such cases.
+
+### Relevant articles
+- More articles [[<-- prev]](/libraries-6)

libraries-7/pom.xml

@@ -0,0 +1,81 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>libraries-7</artifactId>
+
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.agrona</groupId>
+            <artifactId>agrona</artifactId>
+            <version>1.17.1</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <executions>
+                    <execution>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>java</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <includeProjectDependencies>false</includeProjectDependencies>
+                    <includePluginDependencies>true</includePluginDependencies>
+                    <mainClass>uk.co.real_logic.sbe.SbeTool</mainClass>
+                    <systemProperties>
+                        <systemProperty>
+                            <key>sbe.output.dir</key>
+                            <value>${project.build.directory}/generated-sources/java</value>
+                        </systemProperty>
+                    </systemProperties>
+                    <arguments>
+                        <argument>${project.basedir}/src/main/resources/schema.xml</argument>
+                    </arguments>
+                    <workingDirectory>${project.build.directory}/generated-sources/java</workingDirectory>
+                </configuration>
+                <dependencies>
+                    <dependency>
+                        <groupId>uk.co.real-logic</groupId>
+                        <artifactId>sbe-tool</artifactId>
+                        <version>1.27.0</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>build-helper-maven-plugin</artifactId>
+                <version>3.0.0</version>
+                <executions>
+                    <execution>
+                        <id>add-source</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>add-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>${project.build.directory}/generated-sources/java/</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

libraries-7/src/main/java/com/baeldung/sbe/MarketData.java

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+package com.baeldung.sbe;
+
+import java.util.StringJoiner;
+
+import com.baeldung.sbe.stub.Currency;
+import com.baeldung.sbe.stub.Market;
+
+public class MarketData {
+
+    private final int amount;
+    private final double price;
+    private final Market market;
+    private final Currency currency;
+    private final String symbol;
+
+    public MarketData(int amount, double price, Market market, Currency currency, String symbol) {
+        this.amount = amount;
+        this.price = price;
+        this.market = market;
+        this.currency = currency;
+        this.symbol = symbol;
+    }
+
+    public static class Builder {
+        private int amount;
+
+        public Builder amount(int amount) {
+            this.amount = amount;
+            return this;
+        }
+
+        private double price;
+
+        public Builder price(double price) {
+            this.price = price;
+            return this;
+        }
+
+        private Market market;
+
+        public Builder market(Market market) {
+            this.market = market;
+            return this;
+        }
+
+        private Currency currency;
+
+        public Builder currency(Currency currency) {
+            this.currency = currency;
+            return this;
+        }
+
+        private String symbol;
+
+        public Builder symbol(String symbol) {
+            this.symbol = symbol;
+            return this;
+        }
+
+        public MarketData build() {
+            return new MarketData(amount, price, market, currency, symbol);
+        }
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public int getAmount() {
+        return amount;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+
+    public Market getMarket() {
+        return market;
+    }
+
+    public Currency getCurrency() {
+        return currency;
+    }
+
+    public String getSymbol() {
+        return symbol;
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", MarketData.class.getSimpleName() + "[", "]").add("amount=" + amount)
+          .add("price=" + price)
+          .add("market=" + market)
+          .add("currency=" + currency)
+          .add("symbol='" + symbol + "'")
+          .toString();
+    }
+}

libraries-7/src/main/java/com/baeldung/sbe/MarketDataSource.java

@@ -0,0 +1,48 @@
+package com.baeldung.sbe;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.LinkedList;
+
+import com.baeldung.sbe.stub.Currency;
+import com.baeldung.sbe.stub.Market;
+
+public class MarketDataSource implements Iterator<MarketData> {
+
+    private final LinkedList<MarketData> dataQueue = new LinkedList<>();
+
+    public MarketDataSource() {
+        // adding some test data into queue
+        this.dataQueue.addAll(Arrays.asList(MarketData.builder()
+          .amount(1)
+          .market(Market.NASDAQ)
+          .symbol("AAPL")
+          .price(134.12)
+          .currency(Currency.USD)
+          .build(), MarketData.builder()
+          .amount(2)
+          .market(Market.NYSE)
+          .symbol("IBM")
+          .price(128.99)
+          .currency(Currency.USD)
+          .build(), MarketData.builder()
+          .amount(1)
+          .market(Market.NASDAQ)
+          .symbol("AXP")
+          .price(34.87)
+          .currency(Currency.EUR)
+          .build()));
+    }
+
+    @Override
+    public boolean hasNext() {
+        return !this.dataQueue.isEmpty();
+    }
+
+    @Override
+    public MarketData next() {
+        final MarketData data = this.dataQueue.pop();
+        this.dataQueue.add(data);
+        return data;
+    }
+}

libraries-7/src/main/java/com/baeldung/sbe/MarketDataStreamServer.java

@@ -0,0 +1,92 @@
+package com.baeldung.sbe;
+
+import java.nio.ByteBuffer;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class MarketDataStreamServer {
+
+    private static final Logger log = LoggerFactory.getLogger(MarketDataStreamServer.class);
+
+    ByteBuffer buffer = ByteBuffer.allocate(128);
+
+    final AtomicLong writePos = new AtomicLong();
+
+    ScheduledExecutorService writerThread = Executors.newScheduledThreadPool(1);
+    ScheduledExecutorService readerThreadPool = Executors.newScheduledThreadPool(2);
+
+    private class Client {
+
+        final String name;
+        final ByteBuffer readOnlyBuffer;
+
+        final AtomicLong readPos = new AtomicLong();
+
+        Client(String name, ByteBuffer source) {
+            this.name = name;
+            this.readOnlyBuffer = source.asReadOnlyBuffer();
+        }
+
+        void readTradeData() {
+            while (readPos.get() < writePos.get()) {
+                try {
+                    final int pos = this.readOnlyBuffer.position();
+                    final MarketData data = MarketDataUtil.readAndDecode(this.readOnlyBuffer);
+                    readPos.addAndGet(this.readOnlyBuffer.position() - pos);
+                    log.info("<readTradeData> client: {}, read/write gap: {}, data: {}", name, writePos.get() - readPos.get(), data);
+                } catch (IndexOutOfBoundsException e) {
+                    this.readOnlyBuffer.clear(); // ring buffer
+                } catch (Exception e) {
+                    log.error("<readTradeData> cannot read from buffer {}", readOnlyBuffer);
+                }
+            }
+            if (this.readOnlyBuffer.remaining() == 0) {
+                this.readOnlyBuffer.clear(); // ring buffer
+            }
+        }
+
+        void read() {
+            readerThreadPool.scheduleAtFixedRate(this::readTradeData, 1, 1, TimeUnit.SECONDS);
+        }
+    }
+
+    private Client newClient(String name) {
+        return new Client(name, buffer);
+    }
+
+    private void writeTradeData(MarketData data) {
+        try {
+            final int writtenBytes = MarketDataUtil.encodeAndWrite(buffer, data);
+            writePos.addAndGet(writtenBytes);
+            log.info("<writeTradeData> buffer size remaining: %{}, data: {}", 100 * buffer.remaining() / buffer.capacity(), data);
+        } catch (IndexOutOfBoundsException e) {
+            buffer.clear(); // ring buffer
+            writeTradeData(data);
+        } catch (Exception e) {
+            log.error("<writeTradeData> cannot write into buffer {}", buffer);
+        }
+    }
+
+    private void run(MarketDataSource source) {
+        writerThread.scheduleAtFixedRate(() -> {
+            if (source.hasNext()) {
+                writeTradeData(source.next());
+            }
+        }, 1, 2, TimeUnit.SECONDS);
+    }
+
+    public static void main(String[] args) {
+        MarketDataStreamServer server = new MarketDataStreamServer();
+        Client client1 = server.newClient("client1");
+        client1.read();
+        Client client2 = server.newClient("client2");
+        client2.read();
+        server.run(new MarketDataSource());
+    }
+
+}

libraries-7/src/main/java/com/baeldung/sbe/MarketDataUtil.java

@@ -0,0 +1,78 @@
+package com.baeldung.sbe;
+
+import java.math.BigDecimal;
+import java.nio.ByteBuffer;
+
+import org.agrona.concurrent.UnsafeBuffer;
+
+import com.baeldung.sbe.stub.MessageHeaderDecoder;
+import com.baeldung.sbe.stub.MessageHeaderEncoder;
+import com.baeldung.sbe.stub.TradeDataDecoder;
+import com.baeldung.sbe.stub.TradeDataEncoder;
+
+public class MarketDataUtil {
+
+    public static int encodeAndWrite(ByteBuffer buffer, MarketData marketData) {
+
+        final int pos = buffer.position();
+
+        final UnsafeBuffer directBuffer = new UnsafeBuffer(buffer);
+        final MessageHeaderEncoder headerEncoder = new MessageHeaderEncoder();
+        final TradeDataEncoder dataEncoder = new TradeDataEncoder();
+
+        final BigDecimal priceDecimal = BigDecimal.valueOf(marketData.getPrice());
+        final int priceMantis = priceDecimal.scaleByPowerOfTen(priceDecimal.scale())
+          .intValue();
+        final int priceExponent = priceDecimal.scale() * -1;
+
+        final TradeDataEncoder encoder = dataEncoder.wrapAndApplyHeader(directBuffer, pos, headerEncoder);
+        encoder.amount(marketData.getAmount());
+        encoder.quote()
+          .market(marketData.getMarket())
+          .currency(marketData.getCurrency())
+          .symbol(marketData.getSymbol())
+          .price()
+          .mantissa(priceMantis)
+          .exponent((byte) priceExponent);
+
+        // set position
+        final int encodedLength = headerEncoder.encodedLength() + encoder.encodedLength();
+        buffer.position(pos + encodedLength);
+        return encodedLength;
+    }
+
+    public static MarketData readAndDecode(ByteBuffer buffer) {
+
+        final int pos = buffer.position();
+
+        final UnsafeBuffer directBuffer = new UnsafeBuffer(buffer);
+        final MessageHeaderDecoder headerDecoder = new MessageHeaderDecoder();
+        final TradeDataDecoder dataDecoder = new TradeDataDecoder();
+
+        dataDecoder.wrapAndApplyHeader(directBuffer, pos, headerDecoder);
+
+        // set position
+        final int encodedLength = headerDecoder.encodedLength() + dataDecoder.encodedLength();
+        buffer.position(pos + encodedLength);
+
+        final double price = BigDecimal.valueOf(dataDecoder.quote()
+            .price()
+            .mantissa())
+          .scaleByPowerOfTen(dataDecoder.quote()
+            .price()
+            .exponent())
+          .doubleValue();
+
+        return MarketData.builder()
+          .amount(dataDecoder.amount())
+          .symbol(dataDecoder.quote()
+            .symbol())
+          .market(dataDecoder.quote()
+            .market())
+          .currency(dataDecoder.quote()
+            .currency())
+          .price(price)
+          .build();
+    }
+
+}

libraries-7/src/main/resources/schema.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<sbe:messageSchema xmlns:sbe="http://fixprotocol.io/2016/sbe"
+  package="com.baeldung.sbe.stub" id="1" version="0" semanticVersion="5.2" description="A schema represents stock market data.">
+    <types>
+        <composite name="messageHeader" description="Message identifiers and length of message root.">
+            <type name="blockLength" primitiveType="uint16"/>
+            <type name="templateId" primitiveType="uint16"/>
+            <type name="schemaId" primitiveType="uint16"/>
+            <type name="version" primitiveType="uint16"/>
+        </composite>
+        <enum name="Market" encodingType="uint8">
+            <validValue name="NYSE" description="New York Stock Exchange">0</validValue>
+            <validValue name="NASDAQ" description="National Association of Securities Dealers Automated Quotations">1</validValue>
+        </enum>
+        <type name="Symbol" primitiveType="char" length="4" characterEncoding="ASCII" description="Stock symbol"/>
+        <composite name="Decimal">
+            <type name="mantissa" primitiveType="uint64" minValue="0"/>
+            <type name="exponent" primitiveType="int8"/>
+        </composite>
+        <enum name="Currency" encodingType="uint8">
+            <validValue name="USD" description="US Dollar">0</validValue>
+            <validValue name="EUR" description="Euro">1</validValue>
+        </enum>
+        <composite name="Quote" description="A quote represents the price of a stock in a market">
+            <ref name="market" type="Market"/>
+            <ref name="symbol" type="Symbol"/>
+            <ref name="price" type="Decimal"/>
+            <ref name="currency" type="Currency"/>
+        </composite>
+    </types>
+    <sbe:message name="TradeData" id="1" description="Represents a quote and amount of trade">
+        <field name="quote" id="1" type="Quote"/>
+        <field name="amount" id="2" type="uint16"/>
+    </sbe:message>
+</sbe:messageSchema>

libraries-7/src/test/java/com/baeldung/test/EncodeDecodeMarketDataUnitTest.java

@@ -0,0 +1,75 @@
+package com.baeldung.test;
+
+import java.math.BigDecimal;
+import java.nio.ByteBuffer;
+
+import org.agrona.concurrent.UnsafeBuffer;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.sbe.MarketData;
+import com.baeldung.sbe.stub.Currency;
+import com.baeldung.sbe.stub.Market;
+import com.baeldung.sbe.stub.MessageHeaderDecoder;
+import com.baeldung.sbe.stub.MessageHeaderEncoder;
+import com.baeldung.sbe.stub.TradeDataDecoder;
+import com.baeldung.sbe.stub.TradeDataEncoder;
+
+public class EncodeDecodeMarketDataUnitTest {
+
+    private MarketData marketData;
+
+    @BeforeEach
+    public void setup() {
+        marketData = new MarketData(2, 128.99, Market.NYSE, Currency.USD, "IBM");
+    }
+
+    @Test
+    public void givenMarketData_whenEncode_thenDecodedValuesMatch() {
+        // our buffer to write encoded data, initial cap. 128 bytes
+        UnsafeBuffer buffer = new UnsafeBuffer(ByteBuffer.allocate(128));
+        // necessary encoders
+        MessageHeaderEncoder headerEncoder = new MessageHeaderEncoder();
+        TradeDataEncoder dataEncoder = new TradeDataEncoder();
+        // we parse price data (double) into two parts: mantis and exponent
+        BigDecimal priceDecimal = BigDecimal.valueOf(marketData.getPrice());
+        int priceMantissa = priceDecimal.scaleByPowerOfTen(priceDecimal.scale())
+          .intValue();
+        int priceExponent = priceDecimal.scale() * -1;
+        // encode data
+        TradeDataEncoder encoder = dataEncoder.wrapAndApplyHeader(buffer, 0, headerEncoder);
+        encoder.amount(marketData.getAmount());
+        encoder.quote()
+          .market(marketData.getMarket())
+          .currency(marketData.getCurrency())
+          .symbol(marketData.getSymbol())
+          .price()
+          .mantissa(priceMantissa)
+          .exponent((byte) priceExponent);
+
+        // necessary decoders
+        MessageHeaderDecoder headerDecoder = new MessageHeaderDecoder();
+        TradeDataDecoder dataDecoder = new TradeDataDecoder();
+        // decode data
+        dataDecoder.wrapAndApplyHeader(buffer, 0, headerDecoder);
+        // decode price data (from mantissa and exponent) into a double
+        double price = BigDecimal.valueOf(dataDecoder.quote()
+            .price()
+            .mantissa())
+          .scaleByPowerOfTen(dataDecoder.quote()
+            .price()
+            .exponent())
+          .doubleValue();
+        // ensure we have the exact same values
+        Assertions.assertEquals(2, dataDecoder.amount());
+        Assertions.assertEquals("IBM", dataDecoder.quote()
+          .symbol());
+        Assertions.assertEquals(Market.NYSE, dataDecoder.quote()
+          .market());
+        Assertions.assertEquals(Currency.USD, dataDecoder.quote()
+          .currency());
+        Assertions.assertEquals(128.99, price);
+    }
+
+}

pom.xml

@@ -433,6 +433,7 @@
                 <module>language-interop</module>
                 <module>libraries-2</module>
                 <module>libraries-3</module>
+                <module>libraries-7</module>
 
                 <module>libraries-apache-commons</module>
                 <module>libraries-apache-commons-collections</module>