BAEL-1732 - Java with ANTLR (#4243)

Examples for Java with ANTLR article

antlr/pom.xml

@@ -0,0 +1,66 @@
+<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/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>antlr</artifactId>
+    <name>antlr</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.antlr</groupId>
+                <artifactId>antlr4-maven-plugin</artifactId>
+                <version>${antlr.version}</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>antlr4</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>build-helper-maven-plugin</artifactId>
+                <version>${mojo.version}</version>
+                <executions>
+                    <execution>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>add-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>${basedir}/target/generated-sources/antlr4</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+    <dependencies>
+		<dependency>
+			<groupId>org.antlr</groupId>
+			<artifactId>antlr4-runtime</artifactId>
+			<version>${antlr.version}</version>
+		</dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    <properties>
+        <java.version>1.8</java.version>
+        <antlr.version>4.7.1</antlr.version>
+        <junit.version>4.12</junit.version>
+        <mojo.version>3.0.0</mojo.version>
+    </properties>
+</project>

antlr/src/main/antlr4/com/baeldung/antlr/Log.g4

@@ -0,0 +1,16 @@
+grammar Log;
+
+log : entry+;
+entry : timestamp ' ' level ' ' message CRLF;
+timestamp : DATE ' ' TIME;
+level : 'ERROR' | 'INFO' | 'DEBUG';
+message : (TEXT | ' ')+;
+
+fragment DIGIT : [0-9];
+fragment TWODIGIT : DIGIT DIGIT;
+fragment LETTER : [A-Za-z];
+
+DATE : TWODIGIT TWODIGIT '-' LETTER LETTER LETTER '-' TWODIGIT;
+TIME : TWODIGIT ':' TWODIGIT ':' TWODIGIT;
+TEXT : LETTER+;
+CRLF : '\r'? '\n' | '\r';

antlr/src/main/java/com/baeldung/antlr/java/UppercaseMethodListener.java

@@ -0,0 +1,28 @@
+package com.baeldung.antlr.java;
+
+import com.baeldung.antlr.Java8BaseListener;
+import com.baeldung.antlr.Java8Parser;
+import org.antlr.v4.runtime.tree.TerminalNode;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class UppercaseMethodListener extends Java8BaseListener {
+
+    private List<String> errors = new ArrayList<String>();
+
+    @Override
+    public void enterMethodDeclarator(Java8Parser.MethodDeclaratorContext ctx) {
+        TerminalNode node = ctx.Identifier();
+        String methodName = node.getText();
+
+        if (Character.isUpperCase(methodName.charAt(0))){
+            errors.add(String.format("Method %s is uppercased!", methodName));
+        }
+    }
+
+    public List<String> getErrors(){
+        return Collections.unmodifiableList(errors);
+    }
+}

antlr/src/main/java/com/baeldung/antlr/log/LogListener.java

@@ -0,0 +1,51 @@
+package com.baeldung.antlr.log;
+
+import com.baeldung.antlr.LogBaseListener;
+import com.baeldung.antlr.LogParser;
+import com.baeldung.antlr.log.model.LogLevel;
+import com.baeldung.antlr.log.model.LogEntry;
+
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Locale;
+
+public class LogListener extends LogBaseListener {
+
+    private static final DateTimeFormatter DEFAULT_DATETIME_FORMATTER
+            = DateTimeFormatter.ofPattern("yyyy-MMM-dd HH:mm:ss", Locale.ENGLISH);
+
+    private List<LogEntry> entries = new ArrayList<>();
+    private LogEntry currentLogEntry;
+
+    @Override
+    public void enterEntry(LogParser.EntryContext ctx) {
+        this.currentLogEntry = new LogEntry();
+    }
+
+    @Override
+    public void exitEntry(LogParser.EntryContext ctx) {
+        entries.add(currentLogEntry);
+    }
+
+    @Override
+    public void enterTimestamp(LogParser.TimestampContext ctx) {
+        currentLogEntry.setTimestamp(LocalDateTime.parse(ctx.getText(), DEFAULT_DATETIME_FORMATTER));
+    }
+
+    @Override
+    public void enterMessage(LogParser.MessageContext ctx) {
+        currentLogEntry.setMessage(ctx.getText());
+    }
+
+    @Override
+    public void enterLevel(LogParser.LevelContext ctx) {
+        currentLogEntry.setLevel(LogLevel.valueOf(ctx.getText()));
+    }
+
+    public List<LogEntry> getEntries() {
+        return Collections.unmodifiableList(entries);
+    }
+}

antlr/src/main/java/com/baeldung/antlr/log/model/LogEntry.java

@@ -0,0 +1,35 @@
+package com.baeldung.antlr.log.model;
+
+
+import java.time.LocalDateTime;
+
+public class LogEntry {
+
+    private LogLevel level;
+    private String message;
+    private LocalDateTime timestamp;
+
+    public LogLevel getLevel() {
+        return level;
+    }
+
+    public void setLevel(LogLevel level) {
+        this.level = level;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
+
+    public LocalDateTime getTimestamp() {
+        return timestamp;
+    }
+
+    public void setTimestamp(LocalDateTime timestamp) {
+        this.timestamp = timestamp;
+    }
+}

antlr/src/main/java/com/baeldung/antlr/log/model/LogLevel.java

@@ -0,0 +1,5 @@
+package com.baeldung.antlr.log.model;
+
+public enum LogLevel {
+    DEBUG, INFO, ERROR
+}

antlr/src/test/java/com/baeldung/antlr/JavaParserUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.antlr;
+
+import com.baeldung.antlr.java.UppercaseMethodListener;
+import org.antlr.v4.runtime.CharStreams;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.tree.ParseTree;
+import org.antlr.v4.runtime.tree.ParseTreeWalker;
+import org.junit.Test;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class JavaParserUnitTest {
+
+    @Test
+    public void whenOneMethodStartsWithUpperCase_thenOneErrorReturned() throws Exception{
+
+        String javaClassContent = "public class SampleClass { void DoSomething(){} }";
+        Java8Lexer java8Lexer = new Java8Lexer(CharStreams.fromString(javaClassContent));
+        CommonTokenStream tokens = new CommonTokenStream(java8Lexer);
+        Java8Parser java8Parser = new Java8Parser(tokens);
+        ParseTree tree = java8Parser.compilationUnit();
+        ParseTreeWalker walker = new ParseTreeWalker();
+        UppercaseMethodListener uppercaseMethodListener = new UppercaseMethodListener();
+        walker.walk(uppercaseMethodListener, tree);
+
+        assertThat(uppercaseMethodListener.getErrors().size(), is(1));
+        assertThat(uppercaseMethodListener.getErrors().get(0),
+                is("Method DoSomething is uppercased!"));
+    }
+}

antlr/src/test/java/com/baeldung/antlr/LogParserUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.antlr;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import com.baeldung.antlr.log.LogListener;
+import com.baeldung.antlr.log.model.LogLevel;
+import com.baeldung.antlr.log.model.LogEntry;
+import org.antlr.v4.runtime.CharStreams;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.tree.ParseTreeWalker;
+import org.junit.Test;
+
+import java.time.LocalDateTime;
+
+
+public class LogParserUnitTest {
+
+    @Test
+    public void whenLogContainsOneErrorLogEntry_thenOneErrorIsReturned() throws Exception {
+        String logLines = "2018-May-05 14:20:21 DEBUG entering awesome method\r\n" +
+                "2018-May-05 14:20:24 ERROR Bad thing happened\r\n";
+        LogLexer serverLogLexer = new LogLexer(CharStreams.fromString(logLines));
+        CommonTokenStream tokens = new CommonTokenStream( serverLogLexer );
+        LogParser logParser = new LogParser(tokens);
+        ParseTreeWalker walker = new ParseTreeWalker();
+        LogListener logWalker = new LogListener();
+        walker.walk(logWalker, logParser.log());
+
+        assertThat(logWalker.getEntries().size(), is(2));
+        LogEntry error = logWalker.getEntries().get(1);
+        assertThat(error.getLevel(), is(LogLevel.ERROR));
+        assertThat(error.getMessage(), is("Bad thing happened"));
+        assertThat(error.getTimestamp(), is(LocalDateTime.of(2018,5,5,14,20,24)));
+    }
+}

pom.xml

@@ -266,8 +266,9 @@
         <module>twilio</module>
         <module>spring-boot-ctx-fluent</module> 
         <module>java-ee-8-security-api</module>
-	<module>spring-webflux-amqp</module>
+        <module>spring-webflux-amqp</module>
-	<module>maven-archetype</module>
+        <module>antlr</module>
+	      <module>maven-archetype</module>
     </modules>
 
     <dependencies>