Avoid property name collisions when serializing AuditEvent to JSON

Previously, in case the data for the audit event contained an entry
with the key "type", the member `type` from the AuditEvent would be
overwritten when rendering to JSON due to the use of @JsonAnyGetter on
the data property.

This commit removes @JsonAnyGetter so that the data map is rendered as
a separate property in the JSON.

Closes gh-7990

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/AuditEvent.java

@@ -22,7 +22,6 @@ import java.util.Date;
 import java.util.HashMap;
 import java.util.Map;
 
-import com.fasterxml.jackson.annotation.JsonAnyGetter;
 import com.fasterxml.jackson.annotation.JsonFormat;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonInclude.Include;
@@ -137,7 +136,6 @@ public class AuditEvent implements Serializable {
 	 * Returns the event data.
 	 * @return the event data
 	 */
-	@JsonAnyGetter
 	public Map<String, Object> getData() {
 		return this.data;
 	}

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/audit/AuditEventTests.java

@@ -18,10 +18,13 @@ package org.springframework.boot.actuate.audit;
 
 import java.util.Collections;
 
+import org.json.JSONObject;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -74,4 +77,14 @@ public class AuditEventTests {
 		new AuditEvent("phil", null, Collections.singletonMap("a", (Object) "b"));
 	}
 
+	@Test
+	public void jsonFormat() throws Exception {
+		AuditEvent event = new AuditEvent("johannes", "UNKNOWN", Collections.singletonMap("type", (Object) "BadCredentials"));
+
+		String json = Jackson2ObjectMapperBuilder.json().build().writeValueAsString(event);
+		JSONObject jsonObject = new JSONObject(json);
+
+		assertThat(jsonObject.getString("type")).isEqualTo("UNKNOWN");
+	}
+
 }