Add StructuredLogFormatter wrapper for JsonEncoder (logback)

cf-java-logging-support-logback/pom.xml

@@ -25,6 +25,11 @@
             <artifactId>cf-java-logging-support-core</artifactId>
             <version>${project.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot</artifactId>
+            <version>${springboot.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.sap.hcp.cf.logging</groupId>
             <artifactId>cf-java-logging-support-core</artifactId>

cf-java-logging-support-logback/src/main/java/com/sap/hcp/cf/logback/boot/CloudFoundryStructuredLogFormatter.java

@@ -0,0 +1,39 @@
+package com.sap.hcp.cf.logback.boot;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import com.sap.hcp.cf.logback.encoder.JsonEncoder;
+import org.springframework.boot.logging.structured.StructuredLogFormatter;
+
+/**
+ * A Logback events formatter for structured logging in SpringBoot
+ * configuration, suited
+ * for Cloud Foundry applications. This class can be used as a value for
+ * {@code logging.structured.format.console}
+ * or @{code logging.structured.format.file} in a SpringBoot applications.
+ * <p>
+ * This is a simple wrapper around the {@code JsonEncoder} created for Logback.
+ * This formatter does not accept any configuration parameters and uses the default
+ * settings coming with JsonEncoder. The JSON output will contain the same fields 
+ * as produced with {@code JsonEncoder}, but you don't have to use logback.xml 
+ * (or logback-spring.xml) to use it.
+  * <p>
+ * Example usage with SpringBoot ({@code application.properties}):
+ * 
+ * <pre>
+ * logging.structured.format.console = com.sap.hcp.cf.logback.boot.CloudFoundryStructuredLogFormatter
+ * </pre>
+ */
+public class CloudFoundryStructuredLogFormatter implements StructuredLogFormatter<ILoggingEvent> {
+
+    private final JsonEncoder jsonEncoder;
+
+    public CloudFoundryStructuredLogFormatter() {
+        this.jsonEncoder = JsonEncoder.createStarted();
+    }
+
+    @Override
+    public String format(ILoggingEvent event) {
+        return jsonEncoder.getJson(event);
+    }
+
+}

cf-java-logging-support-logback/src/main/java/com/sap/hcp/cf/logback/encoder/JsonEncoder.java

@@ -21,7 +21,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.slf4j.Marker;
-
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.jr.ob.JSON;
 import com.fasterxml.jackson.jr.ob.JSON.Builder;
@@ -78,6 +77,19 @@ public JsonEncoder() {
         logbackContextFieldSuppliers.add(new RequestRecordFieldSupplier());
     }
 
+    /**
+     * Creates a new encoder instance in the {@code started} state, with default settings. 
+     * This means that the encoder is ready to encode log events once this method returns.
+     * 
+     * @return a new {@link JsonEncoder} instance in the started state
+     */
+    public static JsonEncoder createStarted() {
+        JsonEncoder encoder = new JsonEncoder();
+        encoder.start();
+
+        return encoder;
+    }
+
     /**
      * <p>
      * Adds a field to the "#cf" object in the generated output. If the log
@@ -286,7 +298,11 @@ public byte[] encode(ILoggingEvent event) {
         return getJson(event).getBytes(charset);
     }
 
-    private String getJson(ILoggingEvent event) {
+    public String getJson(ILoggingEvent event) {
+        if(!isStarted()) {
+            throw new IllegalStateException("Encoder is not started. Please call start() before encoding.");
+        }
+
         try (StringWriter writer = new StringWriter()) {
             ObjectComposer<JSONComposer<OutputStream>> oc = json.composeTo(writer).startObject();
             addMarkers(oc, event);

cf-java-logging-support-logback/src/test/java/com/sap/hcp/cf/logback/boot/CloudFoundryStructuredLogFormatterTest.java

@@ -0,0 +1,32 @@
+package com.sap.hcp.cf.logback.boot;
+
+import static org.junit.Assert.assertTrue;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.spi.LoggingEvent;
+import org.junit.Test;
+
+public class CloudFoundryStructuredLogFormatterTest {
+
+    CloudFoundryStructuredLogFormatter underTest = new CloudFoundryStructuredLogFormatter();
+
+    @Test
+    public void testFormat() throws Exception {
+        LoggingEvent event = new LoggingEvent();
+        event.setLevel(Level.DEBUG);
+        event.setLoggerName("my-logger");
+        event.setMessage("This is some very important log message");
+        event.setThreadName("thread-1");
+
+        String result = underTest.format(event);
+
+        assertTrue(result.startsWith("{"));
+        assertTrue(result.endsWith("}\n"));
+        assertTrue(result.contains("\"level\":\"DEBUG\""));
+        assertTrue(result.contains("\"logger\":\"my-logger\""));
+        assertTrue(result.contains("\"msg\":\"This is some very important log message\""));
+        assertTrue(result.contains("\"thread\":\"thread-1\""));
+
+    }
+
+}

pom.xml

@@ -147,6 +147,7 @@
         <java-jwt.version>4.4.0</java-jwt.version>
         <jackson-databind.version>2.18.2</jackson-databind.version>
         <httpclient.version>4.5.14</httpclient.version>
+        <springboot.version>3.4.5</springboot.version>
     </properties>
 
     <modules>