Add JSON archive reader.

This archive reader can read archived data from any HTTP server
implementing the JSON archive access protocol as described at
https://oss.aquenos.com/cassandra-pv-archiver/docs/3.2.6/manual/html/apb.html.

In particular, it can retrieve data from the Cassandra PV Archiver and
the JSON Archive Proxy.

app/databrowser-json/pom.xml

@@ -0,0 +1,60 @@
+<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>
+  <parent>
+    <groupId>org.phoebus</groupId>
+    <artifactId>app</artifactId>
+    <version>4.7.4-SNAPSHOT</version>
+  </parent>
+  <artifactId>app-databrowser-json</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter</artifactId>
+      <version>${junit.version}</version>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.hamcrest</groupId>
+      <artifactId>hamcrest-all</artifactId>
+      <version>1.3</version>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.phoebus</groupId>
+      <artifactId>app-databrowser</artifactId>
+      <version>4.7.4-SNAPSHOT</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.phoebus</groupId>
+      <artifactId>core-framework</artifactId>
+      <version>4.7.4-SNAPSHOT</version>
+    </dependency>
+
+    <dependency>
+      <groupId>com.fasterxml.jackson.core</groupId>
+      <artifactId>jackson-core</artifactId>
+      <version>${jackson.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>com.google.guava</groupId>
+      <artifactId>guava</artifactId>
+      <version>${guava.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.epics</groupId>
+      <artifactId>epics-util</artifactId>
+      <version>${epics.util.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.epics</groupId>
+      <artifactId>vtype</artifactId>
+      <version>${vtype.version}</version>
+    </dependency>
+  </dependencies>
+</project>

app/databrowser-json/src/main/java/org/phoebus/archive/reader/json/JsonArchivePreferences.java

@@ -0,0 +1,66 @@
+/*******************************************************************************
+ * Copyright (c) 2024 aquenos GmbH.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ ******************************************************************************/
+
+package org.phoebus.archive.reader.json;
+
+import org.phoebus.framework.preferences.PreferencesReader;
+
+import java.util.logging.Logger;
+
+/**
+ * <p>
+ * Preferences used by the {@link JsonArchiveReader}.
+ * </p>
+ * <p>
+ * Each of the parameters corresponds to a property in the preferences system,
+ * using the <code>org.phoebus.archive.reader.json</code> namespace.
+ * </p>
+ * <p>
+ * Please refer to the <code>archive_reader_json_preferences.properties</code>
+ * file for a full list of available properties and their meanings.
+ * </p>
+ *
+ * @param honor_zero_precision
+ *  flag indicating whether a floating-point value specifying a precision of
+ *  zero shall be printed without any fractional digits (<code>true</code>) or
+ *  whether such a value should be printed using a default format
+ *  (<code>false</code>).
+ */
+public record JsonArchivePreferences(
+        boolean honor_zero_precision) {
+
+    private final static JsonArchivePreferences DEFAULT_INSTANCE;
+
+    static {
+        DEFAULT_INSTANCE = loadPreferences();
+    }
+
+    /**
+     * Returns the default instance of the preferences. This is the instance
+     * that is automatically configured through Phoebus’s
+     * {@link PreferencesReader}.
+     *
+     * @return preference instance created using the {@link PreferencesReader}.
+     */
+    public static JsonArchivePreferences getDefaultInstance() {
+        return DEFAULT_INSTANCE;
+    }
+
+    private static JsonArchivePreferences loadPreferences() {
+        final var logger = Logger.getLogger(
+                JsonArchivePreferences.class.getName());
+        final var preference_reader = new PreferencesReader(
+                JsonArchivePreferences.class,
+                "/archive_reader_json_preferences.properties");
+        final var honor_zero_precision = preference_reader.getBoolean(
+                "honor_zero_precision");
+        logger.config("honor_zero_precision = " + honor_zero_precision);
+        return new JsonArchivePreferences(honor_zero_precision);
+    }
+
+}