com.cloudera.nav.plugin.client.writer.HttpJsonMetadataWriter.java Source code

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Here is the source code for com.cloudera.nav.plugin.client.writer.HttpJsonMetadataWriter.java

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/*
 * Copyright (c) 2015 Cloudera, 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.cloudera.nav.plugin.client.writer;

import com.cloudera.nav.plugin.client.PluginConfigurations;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Throwables;

import java.io.IOException;
import java.io.Writer;
import java.net.HttpURLConnection;
import java.util.Collection;
import java.util.Map;

import org.apache.commons.httpclient.HttpStatus;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Write metadata in JSON format over an HTTP connection
 */
public class HttpJsonMetadataWriter extends MetadataWriter {

    private static final Logger LOG = LoggerFactory.getLogger(HttpJsonMetadataWriter.class);

    private final HttpURLConnection conn;
    private int count;

    public HttpJsonMetadataWriter(PluginConfigurations config, Writer writer, HttpURLConnection conn) {
        super(config, writer);
        this.conn = conn;
        count = 0;
    }

    @Override
    public void begin() {
        try {
            writer.append("[");
            count = 0;
        } catch (IOException e) {
            Throwables.propagate(e);
        }
    }

    @Override
    public void end() {
        try {
            writer.append("]");
        } catch (IOException e) {
            Throwables.propagate(e);
        }
    }

    @Override
    protected void persistMetadataValues(Collection<Map<String, Object>> values) {
        try {
            ObjectMapper mapper = new ObjectMapper();
            for (Map<String, Object> json : values) {
                if (count > 0) {
                    writer.append(",");
                }
                writer.append(mapper.writeValueAsString(json));
                count++;
            }
        } catch (IOException e) {
            Throwables.propagate(e);
        }
    }

    @Override
    public void flush() {
        super.flush();
        try {
            // request is not sent until response code is requested
            if (conn.getResponseCode() >= HttpStatus.SC_BAD_REQUEST) {
                throw new RuntimeException(String.format("Error writing metadata (code %s): %s",
                        conn.getResponseCode(), conn.getResponseMessage()));
            }
        } catch (IOException e) {
            Throwables.propagate(e);
        }
    }
}