com.github.luluvise.droid_utils.json.jackson.JacksonJsonManager.java Source code

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Here is the source code for com.github.luluvise.droid_utils.json.jackson.JacksonJsonManager.java

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/*
 * Copyright 2013 Luluvise Ltd
 *
 * 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.github.luluvise.droid_utils.json.jackson;

import java.io.IOException;

import javax.annotation.CheckForNull;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.guava.GuavaModule;
import com.github.luluvise.droid_utils.logging.LogUtils;
import com.google.api.client.util.ObjectParser;
import com.google.common.annotations.Beta;

/**
 * Singleton class that provides JSON parsing utilities based on the Jackson
 * library for converting POJO (<i>Plain Old Java Objects</i>) data models into
 * JSON.
 * 
 * See {@link http://wiki.fasterxml.com/JacksonHome} for documentation.
 * 
 * Call {@link #registerGuavaModule()} at application startup to enable the
 * {@link GuavaModule} for Jackson.
 * 
 * TODO: do we really need a singleton enum here?
 * 
 * @since 1.0
 * @author Marco Salis
 */
@Beta
@Immutable
public enum JacksonJsonManager {
    INSTANCE;

    private final ObjectMapper mMapper;
    private final JacksonObjectParser mObjParser;

    /**
     * Shortcut method to return the JsonManager singleton
     */
    @Nonnull
    public static JacksonJsonManager get() {
        return INSTANCE;
    }

    /**
     * Private constructor (only used to initialise the singleton fields)
     */
    private JacksonJsonManager() {
        // single global shared ObjectMapper instance
        mMapper = new ObjectMapper();
        // global setting to write dates in ISO8601 format (not needed for now)
        // mMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,
        // false);
        mObjParser = new JacksonObjectParser(mMapper);
    }

    /**
     * Register {@link GuavaModule} module for Guava data structures
     */
    public static void registerGuavaModule() {
        INSTANCE.mMapper.registerModule(new GuavaModule());
    }

    /**
     * Returns the global {@link ObjectParser} instance associated with the
     * {@link ObjectMapper}
     * 
     * @return The {@link JacksonObjectParser} parser
     */
    @Nonnull
    public static JacksonObjectParser getObjectParser() {
        return INSTANCE.mObjParser;
    }

    /**
     * Returns the global {@link ObjectMapper}
     * 
     * @return The {@link ObjectMapper}
     */
    @Nonnull
    public static ObjectMapper getObjectMapper() {
        return INSTANCE.mMapper;
    }

    /**
     * Builds a new {@link JacksonHttpContent} from the source object.
     * 
     * @param source
     *            The source object (keys must be specified for the mapping to
     *            work)
     * @return The built {@link JacksonHttpContent}
     */
    public static JacksonHttpContent buildHttpContent(@Nonnull Object source) {
        return new JacksonHttpContent(source);
    }

    /**
     * Shortcut method to parse a POJO object into a JSON string
     * 
     * @param data
     *            The object to parse
     * @return The string representation of that object (or null if the parse
     *         failed for an IOException)
     */
    @CheckForNull
    public static String toString(Object data) {
        try {
            return INSTANCE.mMapper.writeValueAsString(data);
        } catch (IOException e) {
            LogUtils.logException(e);
            return null;
        }
    }

}