Update java plugin docs for beta (#10534)

docs/static/java-output.asciidoc

@@ -15,7 +15,7 @@
 [[java-output-plugin]]
 === How to write a Java output plugin
 
-experimental[]
+beta[]
 
 // Pulls in shared section: Setting Up Environment
 include::include/javapluginsetup.asciidoc[]
@@ -23,41 +23,39 @@ include::include/javapluginsetup.asciidoc[]
 [float]
 === Code the plugin
 
-The example output plugin prints events in JSON format to the console. Let's
-look at the main class in that example output:
+The example output plugin prints events to the console using the event's
+`toString` method. Let's look at the main class in the example output:
  
 [source,java]
 -----
-@LogstashPlugin(name="java_output_example")
+@LogstashPlugin(name = "java_output_example")
 public class JavaOutputExample implements Output {
 
     public static final PluginConfigSpec<String> PREFIX_CONFIG =
-            Configuration.stringSetting("prefix", "");
+            PluginConfigSpec.stringSetting("prefix", "");
 
+    private final String id;
     private String prefix;
     private PrintStream printer;
     private final CountDownLatch done = new CountDownLatch(1);
     private volatile boolean stopped = false;
 
-    public JavaOutputExample(final Configuration configuration, final Context context) {
-        this(configuration, context, System.out);
+    public JavaOutputExample(final String id, final Configuration configuration, final Context context) {
+        this(id, configuration, context, System.out);
     }
 
-    JavaOutputExample(final Configuration config, final Context context, OutputStream targetStream) {
+    JavaOutputExample(final String id, final Configuration config, final Context context, OutputStream targetStream) {
+        this.id = id;
         prefix = config.get(PREFIX_CONFIG);
         printer = new PrintStream(targetStream);
     }
 
     @Override
     public void output(final Collection<Event> events) {
-        try {
-            Iterator<Event> z = events.iterator();
-            while (z.hasNext() && !stopped) {
-                String s = prefix + z.next().toJson();
-                printer.println(s);
-            }
-        } catch (JsonProcessingException e) {
-            throw new IllegalStateException(e);
+      Iterator<Event> z = events.iterator();
+      while (z.hasNext() && !stopped) {
+          String s = prefix + z.next();
+          printer.println(s);
         }
     }
 
@@ -76,6 +74,11 @@ public class JavaOutputExample implements Output {
     public Collection<PluginConfigSpec<?>> configSchema() {
         return Collections.singletonList(PREFIX_CONFIG);
     }
+  
+    @Override
+    public String getId() {
+        return id;
+    }
 }
 -----
 
@@ -97,7 +100,7 @@ Notes about the class declaration:
    in the Logstash pipeline definition. For example, this output would be referenced in the output section of the
    Logstash pipeline definition as `output { java_output_example => { .... } }`
 ** The value of the `name` property must match the name of the class excluding casing and underscores.
-* The class must implement the `co.elastic.logstash.api.v0.Output` interface.
+* The class must implement the `co.elastic.logstash.api.Output` interface.
 
 [float]
 ==== Plugin settings
@@ -107,7 +110,7 @@ The snippet below contains both the setting definition and the method referencin
 [source,java]
 -----
 public static final PluginConfigSpec<String> PREFIX_CONFIG =
-        Configuration.stringSetting("prefix", "");
+        PluginConfigSpec.stringSetting("prefix", "");
 
 @Override
 public Collection<PluginConfigSpec<?>> configSchema() {
@@ -131,26 +134,28 @@ unsupported settings are present.
 
 [source,java]
 -----
+private final String id;
 private String prefix;
 private PrintStream printer;
 
-public JavaOutputExample(final Configuration configuration, final Context context) {
+public JavaOutputExample(final String id, final Configuration configuration, final Context context) {
     this(configuration, context, System.out);
 }
 
-JavaOutputExample(final Configuration config, final Context context, OutputStream targetStream) {
+JavaOutputExample(final String id, final Configuration config, final Context context, OutputStream targetStream) {
+    this.id = id;
     prefix = config.get(PREFIX_CONFIG);
     printer = new PrintStream(targetStream);
 }
 -----
 
-All Java output plugins must have a constructor taking both a `Configuration`
-and `Context` argument. This is the constructor that will be used to instantiate
-them at runtime. The retrieval and validation of all plugin settings should
-occur in this constructor. In this example, the values of the `prefix` setting
-is retrieved and stored in a local variable for later use in the `output`
-method. In this example, a second, pacakge private constructor is defined that
-is useful for unit testing with a `Stream` other than `System.out`.
+All Java output plugins must have a constructor taking a `String` id and a
+`Configuration` and `Context` argument. This is the constructor that will be
+used to instantiate them at runtime. The retrieval and validation of all plugin
+settings should occur in this constructor. In this example, the values of the
+`prefix` setting is retrieved and stored in a local variable for later use in
+the `output` method. In this example, a second, pacakge private constructor is
+defined that is useful for unit testing with a `Stream` other than `System.out`.
 
 Any additional initialization may occur in the constructor as well. If there are
 any unrecoverable errors encountered in the configuration or initialization of
@@ -164,14 +169,10 @@ be logged and will prevent Logstash from starting.
 -----
 @Override
 public void output(final Collection<Event> events) {
-    try {
-        Iterator<Event> z = events.iterator();
-        while (z.hasNext() && !stopped) {
-            String s = prefix + z.next().toJson();
-            printer.println(s);
-        }
-    } catch (JsonProcessingException e) {
-        throw new IllegalStateException(e);
+    Iterator<Event> z = events.iterator();
+    while (z.hasNext() && !stopped) {
+        String s = prefix + z.next();
+        printer.println(s);
     }
 }
 -----
@@ -210,6 +211,20 @@ should **not** signal the output to stop as the `stop` method  does. The
 awaitStop mechanism may be implemented in any way that honors the API contract
 though a `CountDownLatch` works well for many use cases.
 
+[float]
+==== getId method
+
+[source,java]
+-----
+@Override
+public String getId() {
+    return id;
+}
+-----
+
+For output plugins, the `getId` method should always return the id that was provided to the plugin through its
+constructor at instantiation time.
+
 [float]
 ==== Unit tests