[BAEL-2111] guest | Why SLF4J? 10 Reasons to use it (eugenp#5536)

*  Added new submodule for SLF4J guest post, containg modules for logback, log4j and log4j2

* * added tests for logging endpoints
* removed application tests, no use now that we have other tests

guest/slf4j/guide/pom.xml

@@ -0,0 +1,64 @@
+<?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>
+
+    <groupId>com.stackify.slf4j.guide</groupId>
+    <artifactId>slf4j-parent-module</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.0.6.RELEASE</version>
+    </parent>
+
+    <modules>
+        <module>slf4j-logback</module>
+        <module>slf4j-log4j2</module>
+        <module>slf4j-log4j</module>
+    </modules>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-module-junit4</artifactId>
+            <version>${powermock.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-api-mockito2</artifactId>
+            <version>${powermock.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+        <java.version>1.8</java.version>
+        <powermock.version>2.0.0-beta.5</powermock.version>
+    </properties>
+</project>

guest/slf4j/guide/slf4j-log4j/.gitignore

@@ -0,0 +1,25 @@
+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/build/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

guest/slf4j/guide/slf4j-log4j/pom.xml

@@ -0,0 +1,41 @@
+<?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>slf4j-log4j</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.stackify.slf4j.guide</groupId>
+        <artifactId>slf4j-parent-module</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.springframework.boot</groupId>
+                    <artifactId>spring-boot-starter-logging</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    <properties>
+        <slf4j.log4j.version>1.7.25</slf4j.log4j.version>
+    </properties>
+</project>

guest/slf4j/guide/slf4j-log4j/src/main/java/com/stackify/slf4j/guide/Application.java

@@ -0,0 +1,12 @@
+package com.stackify.slf4j.guide;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class Application {
+
+	public static void main(String[] args) {
+		SpringApplication.run(Application.class, args);
+	}
+}

guest/slf4j/guide/slf4j-log4j/src/main/java/com/stackify/slf4j/guide/controllers/SimpleController.java

@@ -0,0 +1,42 @@
+package com.stackify.slf4j.guide.controllers;
+
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class SimpleController {
+
+    Logger logger = LoggerFactory.getLogger(SimpleController.class);
+
+    @GetMapping("/slf4j-guide-request")
+    public String processList(List<String> list) {
+        logger.info("Client requested process the following list: {}", list);
+        try {
+            logger.debug("Starting process");
+            // ...processing list here...
+            Thread.sleep(500);
+        } catch (RuntimeException | InterruptedException e) {
+            logger.error("There was an issue processing the list.", e);
+        } finally {
+            logger.info("Finished processing");
+        }
+        return "done";
+    }
+
+    @GetMapping("/slf4j-guide-mdc-request")
+    public String clientMDCRequest(@RequestHeader String clientId) throws InterruptedException {
+        MDC.put("clientId", clientId);
+        logger.info("Client {} has made a request", clientId);
+        logger.info("Starting request");
+        Thread.sleep(500);
+        logger.info("Finished request");
+        MDC.clear();
+        return "finished";
+    }
+}

guest/slf4j/guide/slf4j-log4j/src/main/resources/log4j.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
+
+<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
+  <appender name="console" class="org.apache.log4j.ConsoleAppender"> 
+    <param name="Target" value="System.out"/> 
+    <layout class="org.apache.log4j.PatternLayout"> 
+      <param name="ConversionPattern" value="%5p %d{ISO8601} [%X{clientId}@%t][%x] %c - %m%n"/> 
+    </layout> 
+  </appender> 
+
+  <root> 
+    <priority value ="info" /> 
+    <appender-ref ref="console" /> 
+  </root>
+
+</log4j:configuration>

guest/slf4j/guide/slf4j-log4j/src/test/java/com/stackify/slf4j/guide/controllers/SimpleControllerIntegrationTest.java

@@ -0,0 +1,80 @@
+package com.stackify.slf4j.guide.controllers;
+
+import static org.powermock.api.mockito.PowerMockito.doNothing;
+import static org.powermock.api.mockito.PowerMockito.spy;
+
+import java.util.Collections;
+
+import org.apache.log4j.Level;
+import org.apache.log4j.spi.LoggingEvent;
+import org.assertj.core.api.Condition;
+import org.assertj.core.api.SoftAssertions;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+import org.slf4j.MDC;
+
+import com.stackify.slf4j.guide.utils.ListAppender;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest(MDC.class)
+public class SimpleControllerIntegrationTest {
+
+    private SimpleController controller = new SimpleController();
+
+    @Before
+    public void clearLogList() {
+        ListAppender.clearEventList();
+    }
+
+    @Test
+    public void whenSimpleRequestMade_thenAllRegularMessagesLogged() {
+        String output = controller.processList(Collections.emptyList());
+
+        SoftAssertions errorCollector = new SoftAssertions();
+        errorCollector.assertThat(ListAppender.getEvents())
+            .haveAtLeastOne(eventContains("Client requested process the following list: []", Level.INFO))
+            .haveAtLeastOne(eventContains("Starting process", Level.DEBUG))
+            .haveAtLeastOne(eventContains("Finished processing", Level.INFO))
+            .haveExactly(0, eventOfLevel(Level.ERROR));
+        errorCollector.assertThat(output)
+            .isEqualTo("done");
+        errorCollector.assertAll();
+    }
+
+    @Test
+    public void givenClientId_whenMDCRequestMade_thenMessagesWithClientIdLogged() throws Exception {
+        // We avoid cleaning the context so tht we can check it afterwards
+        spy(MDC.class);
+        doNothing().when(MDC.class);
+        MDC.clear();
+        String clientId = "id-1234";
+
+        String output = controller.clientMDCRequest(clientId);
+
+        SoftAssertions errorCollector = new SoftAssertions();
+        errorCollector.assertThat(ListAppender.getEvents())
+            .allMatch(entry -> {
+                return clientId.equals(entry.getMDC("clientId"));
+            })
+            .haveAtLeastOne(eventContains("Client id-1234 has made a request", Level.INFO))
+            .haveAtLeastOne(eventContains("Starting request", Level.INFO))
+            .haveAtLeastOne(eventContains("Finished request", Level.INFO));
+        errorCollector.assertThat(output)
+            .isEqualTo("finished");
+        errorCollector.assertAll();
+
+    }
+
+    private Condition<LoggingEvent> eventOfLevel(Level level) {
+        return eventContains(null, level);
+    }
+
+    private Condition<LoggingEvent> eventContains(String substring, Level level) {
+
+        return new Condition<LoggingEvent>(entry -> (substring == null || (entry.getRenderedMessage() != null && entry.getRenderedMessage()
+            .contains(substring))) && (level == null || level.equals(entry.getLevel())), String.format("entry with message '%s', level %s", substring, level));
+    }
+}

guest/slf4j/guide/slf4j-log4j/src/test/java/com/stackify/slf4j/guide/utils/ListAppender.java

@@ -0,0 +1,33 @@
+package com.stackify.slf4j.guide.utils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.log4j.AppenderSkeleton;
+import org.apache.log4j.spi.LoggingEvent;
+
+public class ListAppender extends AppenderSkeleton {
+    public static List<LoggingEvent> events = new ArrayList<LoggingEvent>();
+
+    @Override
+    public void close() {
+    }
+
+    @Override
+    public boolean requiresLayout() {
+        return false;
+    }
+
+    @Override
+    protected void append(LoggingEvent event) {
+        events.add(event);
+    }
+
+    public static List<LoggingEvent> getEvents() {
+        return events;
+    }
+
+    public static void clearEventList() {
+        events.clear();
+    }
+}

guest/slf4j/guide/slf4j-log4j/src/test/resources/log4j.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
+
+<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
+  <appender name="console" class="org.apache.log4j.ConsoleAppender"> 
+    <param name="Target" value="System.out"/> 
+  </appender>
+  <appender name="list" class="com.stackify.slf4j.guide.utils.ListAppender">
+  </appender> 
+
+  <root> 
+    <priority value ="trace" /> 
+    <appender-ref ref="list" /> 
+  </root>
+
+</log4j:configuration>

guest/slf4j/guide/slf4j-log4j2/.gitignore

@@ -0,0 +1,25 @@
+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/build/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/