/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.datastax.driver.examples.json;
import com.datastax.driver.core.*;
import com.datastax.driver.extras.codecs.json.Jsr353JsonCodec;
import javax.json.Json;
import javax.json.JsonObject;
import javax.json.JsonStructure;
import static com.datastax.driver.core.querybuilder.QueryBuilder.*;
/**
* Illustrates how to map an entire table row to a Java object using
* the <a href="https://jcp.org/en/jsr/detail?id=353">Java API for JSON processing</a>,
* and leveraging the {@code SELECT JSON} and {@code INSERT JSON} syntaxes
* introduced in Cassandra 2.2.
* <p/>
* This example makes usage of a custom {@link TypeCodec codec},
* {@link Jsr353JsonCodec}, which is declared in the driver-extras module.
* If you plan to follow this example, make sure to include the following
* Maven dependencies in your project:
* <pre>{@code
* <dependency>
* <groupId>com.datastax.cassandra</groupId>
* <artifactId>cassandra-driver-extras</artifactId>
* <version>${driver.version}</version>
* </dependency>
*
* <dependency>
* <groupId>javax.json</groupId>
* <artifactId>javax.json-api</artifactId>
* <version>${jsr353-api.version}</version>
* </dependency>
*
* <dependency>
* <groupId>org.glassfish</groupId>
* <artifactId>javax.json</artifactId>
* <version>${jsr353-ri.version}</version>
* <scope>runtime</scope>
* </dependency>
* }</pre>
* This example also uses the {@link com.datastax.driver.core.querybuilder.QueryBuilder QueryBuilder};
* for examples using the "core" API, see {@link PlainTextJson} (they are easily translatable to the
* queries in this class).
* <p/>
* Preconditions:
* - a Cassandra 2.2+ cluster is running and accessible through the contacts points identified by CONTACT_POINTS and PORT;
* <p/>
* Side effects:
* - creates a new keyspace "examples" in the cluster. If a keyspace with this name already exists, it will be reused;
* - creates a table "examples.json_jsr353_row". If it already exists, it will be reused;
* - inserts data in the table.
*
* @see <a href="http://www.datastax.com/dev/blog/whats-new-in-cassandra-2-2-json-support">What’s New in Cassandra 2.2: JSON Support</a>
*/
public class Jsr353JsonRow {
static String[] CONTACT_POINTS = {"127.0.0.1"};
static int PORT = 9042;
public static void main(String[] args) {
Cluster cluster = null;
try {
// A codec to convert JSON payloads into JsonObject instances;
// this codec is declared in the driver-extras module
Jsr353JsonCodec userCodec = new Jsr353JsonCodec();
cluster = Cluster.builder()
.addContactPoints(CONTACT_POINTS).withPort(PORT)
.withCodecRegistry(new CodecRegistry().register(userCodec))
.build();
Session session = cluster.connect();
createSchema(session);
insertJsonRow(session);
selectJsonRow(session);
} finally {
if (cluster != null) cluster.close();
}
}
private static void createSchema(Session session) {
session.execute("CREATE KEYSPACE IF NOT EXISTS examples " +
"WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1}");
session.execute("CREATE TABLE IF NOT EXISTS examples.json_jsr353_row(" +
"id int PRIMARY KEY, name text, age int)");
}
// Mapping a User instance to a table row using INSERT JSON
private static void insertJsonRow(Session session) {
JsonObject alice = Json.createObjectBuilder()
.add("id", 1)
.add("name", "alice")
.add("age", 30)
.build();
JsonObject bob = Json.createObjectBuilder()
.add("id", 2)
.add("name", "bob")
.add("age", 35)
.build();
// Build and execute a simple statement
Statement stmt = insertInto("examples", "json_jsr353_row")
.json(alice);
session.execute(stmt);
// The JSON object can be a bound value if the statement is prepared
// (we use a local variable here for the sake of example, but in a real application you would cache and reuse
// the prepared statement)
PreparedStatement pst = session.prepare(
insertInto("examples", "json_jsr353_row").json(bindMarker("user")));
session.execute(pst.bind()
// note that the codec requires that the type passed to the set() method
// be always JsonStructure, and not a subclass of it, such as JsonObject
.set("user", bob, JsonStructure.class));
}
// Retrieving User instances from table rows using SELECT JSON
private static void selectJsonRow(Session session) {
// Reading the whole row as a JSON object
Statement stmt = select().json()
.from("examples", "json_jsr353_row")
.where(in("id", 1, 2));
ResultSet rows = session.execute(stmt);
for (Row row : rows) {
// SELECT JSON returns only one column for each row, of type VARCHAR,
// containing the row as a JSON payload.
// Note that the codec requires that the type passed to the get() method
// be always JsonStructure, and not a subclass of it, such as JsonObject,
// hence the need to downcast to JsonObject manually
JsonObject user = (JsonObject) row.get(0, JsonStructure.class);
System.out.printf("Retrieved user: %s%n", user);
}
}
}