Add support for handling JSON input.

org.jgrapes.io/build.gradle

@@ -1,6 +1,7 @@
 dependencies {
     api project(':org.jgrapes.core')
 	api project(':org.jgrapes.util')
+    api 'com.fasterxml.jackson.core:jackson-databind:[2.13,3)'
 }
 
 sourceSets {

org.jgrapes.io/src/org/jgrapes/io/util/JsonReader.java

@@ -0,0 +1,74 @@
+/*
+ * JGrapes Event Driven Framework
+ * Copyright (C) 2022 Michael N. Lipp
+ * 
+ * This program is free software; you can redistribute it and/or modify it 
+ * under the terms of the GNU General Public License as published by 
+ * the Free Software Foundation; either version 3 of the License, or 
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but 
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
+ * for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along 
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.jgrapes.io.util;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.jgrapes.core.Channel;
+import org.jgrapes.core.EventPipeline;
+import org.jgrapes.io.util.events.DataInput;
+import org.jgrapes.io.util.events.JsonParsingError;
+
+/**
+ * A {@link ManagedBufferStreamer} that feeds the data to a JSON parser.
+ * When the data is fully parsed, it is made available by firing a
+ * {@link DataInput} event.
+ * 
+ * @since 2.8
+ */
+@SuppressWarnings("PMD.DataflowAnomalyAnalysis")
+public class JsonReader extends ManagedBufferStreamer {
+
+    /**
+     * Instantiates a new JSON reader.
+     *
+     * @param <R> the result data type
+     * @param mapper the mapper
+     * @param resultType the result type
+     * @param pipeline the pipeline to use for sending the
+     * {@link DataInput} event
+     * @param channel the channel to use for sending the 
+     * {@link DataInput} event
+     */
+    public <R> JsonReader(ObjectMapper mapper, Class<R> resultType,
+            EventPipeline pipeline, Channel channel) {
+        super(r -> {
+            try {
+                pipeline.fire(new DataInput<R>(mapper.readValue(r, resultType)),
+                    channel);
+            } catch (Exception e) {
+                pipeline.fire(new JsonParsingError(e), channel);
+            }
+        });
+    }
+
+    /**
+     * Instantiates a new JSON reader that uses a default object mapper.
+     *
+     * @param <R> the result data type
+     * @param resultType the result type
+     * @param pipeline the pipeline to use for sending the
+     * {@link DataInput} event
+     * @param channel the channel to use for sending the
+     * {@link DataInput} event
+     */
+    public <R> JsonReader(Class<R> resultType, EventPipeline pipeline,
+            Channel channel) {
+        this(new ObjectMapper(), resultType, pipeline, channel);
+    }
+}

org.jgrapes.io/src/org/jgrapes/io/util/events/DataInput.java

@@ -0,0 +1,50 @@
+/*
+ * JGrapes Event Driven Framework
+ * Copyright (C) 2024 Michael N. Lipp
+ * 
+ * This program is free software; you can redistribute it and/or modify it 
+ * under the terms of the GNU Affero General Public License as published by 
+ * the Free Software Foundation; either version 3 of the License, or 
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but 
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License 
+ * for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License along 
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.jgrapes.io.util.events;
+
+import org.jgrapes.core.Event;
+
+/**
+ * Signals that some data is available for handling.
+ * 
+ * @param <T>
+ */
+public class DataInput<T> extends Event<Void> {
+
+    private T data;
+
+    /**
+     * Instantiates a new data input providing the given data.
+     *
+     * @param data the data
+     */
+    public DataInput(T data) {
+        this.data = data;
+    }
+
+    /**
+     * Gets the data.
+     *
+     * @return the data
+     */
+    public T data() {
+        return data;
+    }
+
+}

org.jgrapes.io/src/org/jgrapes/io/util/events/JsonParsingError.java

@@ -0,0 +1,37 @@
+/*
+ * JGrapes Event Driven Framework
+ * Copyright (C) 2024 Michael N. Lipp
+ * 
+ * This program is free software; you can redistribute it and/or modify it 
+ * under the terms of the GNU Affero General Public License as published by 
+ * the Free Software Foundation; either version 3 of the License, or 
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but 
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License 
+ * for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License along 
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.jgrapes.io.util.events;
+
+import org.jgrapes.core.events.Error;
+
+/**
+ * Signals an error that occurred while parsing JSON.
+ */
+public class JsonParsingError extends Error {
+
+    /**
+     * Instantiates a new JSON parsing error.
+     *
+     * @param throwable the throwable
+     */
+    public JsonParsingError(Throwable throwable) {
+        super(null, throwable);
+    }
+
+}

org.jgrapes.io/src/org/jgrapes/io/util/events/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * Events associated with classes from {@link org.jgrapes.io.util}.
+ */
+
+package org.jgrapes.io.util.events;

org.jgrapes.io/test/org/jgrapes/io/test/JsonReaderTests.java

@@ -0,0 +1,69 @@
+package org.jgrapes.io.test;
+
+import java.io.IOException;
+import java.nio.CharBuffer;
+import java.util.Map;
+import org.jgrapes.core.Channel;
+import org.jgrapes.core.Component;
+import org.jgrapes.core.Components;
+import org.jgrapes.core.annotation.Handler;
+import org.jgrapes.core.events.Started;
+import org.jgrapes.io.util.JsonReader;
+import org.jgrapes.io.util.ManagedBuffer;
+import org.jgrapes.io.util.ManagedBufferPool;
+import org.jgrapes.io.util.events.DataInput;
+import static org.junit.Assert.*;
+import org.junit.Test;
+
+public class JsonReaderTests {
+
+    public class TestApp extends Component {
+
+        @Handler
+        public void onStarted(Started event, Channel channel)
+                throws InterruptedException, IOException {
+            registerAsGenerator();
+            var charBufferPool = new ManagedBufferPool<>(ManagedBuffer::new,
+                () -> CharBuffer.allocate(4096), 2).setName("Test");
+
+            // Create reader
+            JsonReader rdr
+                = new JsonReader(Object.class, activeEventPipeline(), this);
+
+            // Feed
+            var data = charBufferPool.acquire();
+            data.backingBuffer().append("{\"hello\": \"world\"}");
+            data.backingBuffer().flip();
+            rdr.feed(data);
+            data.unlockBuffer();
+
+            // End of feed
+            rdr.feed(null);
+        }
+
+        @Handler
+        public void onJson(DataInput<Object> event, Channel channel) {
+            result = event.data();
+            unregisterAsGenerator();
+        }
+    }
+
+    private Object result;
+
+    @SuppressWarnings("unchecked")
+    @Test(timeout = 1000)
+    public void test() throws InterruptedException, IOException {
+
+        var app = new TestApp();
+        Components.start(app);
+
+        while (result == null) {
+            Thread.sleep(10);
+        }
+        assertTrue(result instanceof Map);
+        assertEquals("world", ((Map<String, String>) result).get("hello"));
+
+        Components.awaitExhaustion();
+    }
+
+}