RandomSec/main/src/com/google/refine/importers/JsonImporter.java

/*

Copyright 2010, Google Inc.
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    * Redistributions of source code must retain the above copyright
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    * Redistributions in binary form must reproduce the above
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contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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*/

package com.google.refine.importers;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.List;

import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.JsonToken;
import org.json.JSONArray;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.refine.ProjectMetadata;
import com.google.refine.importers.tree.ImportColumnGroup;
import com.google.refine.importers.tree.TreeImportingParserBase;
import com.google.refine.importers.tree.TreeReader;
import com.google.refine.importers.tree.TreeReaderException;
import com.google.refine.importing.ImportingJob;
import com.google.refine.importing.ImportingUtilities;
import com.google.refine.model.Project;
import com.google.refine.util.JSONUtilities;

public class JsonImporter extends TreeImportingParserBase {
    static final Logger logger = LoggerFactory.getLogger(JsonImporter.class);

    public JsonImporter() {
        super(false);
    }
    
    static private class PreviewParsingState {
        int tokenCount;
    }
    
    final static private int PREVIEW_PARSING_LIMIT = 1000;
    
    @Override
    public JSONObject createParserUIInitializationData(
            ImportingJob job, List<JSONObject> fileRecords, String format) {
        JSONObject options = super.createParserUIInitializationData(job, fileRecords, format);
        if (fileRecords.size() > 0) {
            try {
                JSONObject firstFileRecord = fileRecords.get(0);
                File file = ImportingUtilities.getFile(job, firstFileRecord);
                InputStream is = new FileInputStream(file);
                try {
                    JsonFactory factory = new JsonFactory();
                    JsonParser parser = factory.createJsonParser(is);

                    PreviewParsingState state = new PreviewParsingState();
                    Object rootValue = parseForPreview(parser, state);
                    if (rootValue != null) {
                        JSONUtilities.safePut(options, "dom", rootValue);
                    }
                } finally {
                    is.close();
                }
            } catch (IOException e) {
                logger.error("Error generating parser UI initialization data for JSON file", e);
            }
        }

        return options;
    }
    
    final static private Object parseForPreview(JsonParser parser, PreviewParsingState state, JsonToken token)
            throws JsonParseException, IOException {
        if (token != null) {
            switch (token) {
            case START_ARRAY:
                return parseArrayForPreview(parser, state);
            case START_OBJECT:
                return parseObjectForPreview(parser, state);
            case VALUE_STRING:
                return parser.getText();
            case VALUE_NUMBER_INT:
                return Integer.valueOf(parser.getIntValue());
            case VALUE_NUMBER_FLOAT:
                return Float.valueOf(parser.getFloatValue());
            case VALUE_TRUE:
                return Boolean.TRUE;
            case VALUE_FALSE:
                return Boolean.FALSE;
            case VALUE_NULL:
                return null;
            }
        }
        return null;
    }
    
    final static private Object parseForPreview(JsonParser parser, PreviewParsingState state) {
        try {
            JsonToken token = parser.nextToken();
            state.tokenCount++;
            return parseForPreview(parser, state, token);
        } catch (IOException e) {
            return null;
        }
    }
    
    final static private JSONObject parseObjectForPreview(JsonParser parser, PreviewParsingState state) {
        JSONObject result = new JSONObject();
        loop:while (state.tokenCount < PREVIEW_PARSING_LIMIT) {
            try {
                JsonToken token = parser.nextToken();
                if (token == null) {
                    break;
                }
                state.tokenCount++;
                
                switch (token) {
                case FIELD_NAME:
                    String fieldName = parser.getText();
                    Object fieldValue = parseForPreview(parser, state);
                    JSONUtilities.safePut(result, fieldName, fieldValue);
                    break;
                case END_OBJECT:
                    break loop;
                default:
                    break loop;
                }
            } catch (IOException e) {
                break;
            }
        }
        return result;
    }
    
    final static private JSONArray parseArrayForPreview(JsonParser parser, PreviewParsingState state) {
        JSONArray result = new JSONArray();
        loop:while (state.tokenCount < PREVIEW_PARSING_LIMIT) {
            try {
                JsonToken token = parser.nextToken();
                if (token == null) {
                    break;
                }
                state.tokenCount++;
                
                switch (token) {
                case END_ARRAY:
                    break loop;
                default:
                    Object element = parseForPreview(parser, state, token);
                    JSONUtilities.append(result, element);
                }
            } catch (IOException e) {
                break;
            }
        }
        return result;
    }
    
    @Override
    public void parseOneFile(Project project, ProjectMetadata metadata,
            ImportingJob job, String fileSource, Reader reader,
            ImportColumnGroup rootColumnGroup, int limit, JSONObject options, List<Exception> exceptions) {
        
        parseOneFile(project, metadata, job, fileSource,
            new JSONTreeReader(reader), rootColumnGroup, limit, options, exceptions);
    }
    
    static public class JSONTreeReader implements TreeReader {
        final static Logger logger = LoggerFactory.getLogger("JsonParser");
        
        JsonFactory factory = new JsonFactory();
        JsonParser parser = null;
        
        //The following is a workaround for inconsistent Jackson JsonParser
        Boolean lastTokenWasAFieldNameAndCurrentTokenIsANewEntity = false;
        Boolean thisTokenIsAFieldName = false;
        String lastFieldName = null;
        //end of workaround
        
        public JSONTreeReader(Reader reader) {
            try {
                parser = factory.createJsonParser(reader);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        
        /**
         * Does nothing. All Json is treated as elements
         */
        @Override
        public int getAttributeCount() {
            return 0;
        }
        
        /**
         * Does nothing. All Json is treated as elements
         */
        @Override
        public String getAttributeLocalName(int index) {
            return null;
        }

        /**
         * Does nothing. All Json is treated as elements
         */
        @Override
        public String getAttributePrefix(int index) {
            return null;
        }

        /**
         * Does nothing. All Json is treated as elements
         */
        @Override
        public String getAttributeValue(int index) {
            return null;
        }

        @Override
        public Token current() {
            return this.mapToToken(parser.getCurrentToken());
        }

        @Override
        public String getFieldName() throws TreeReaderException {
            try {
                String text = parser.getCurrentName();
                
                //The following is a workaround for inconsistent Jackson JsonParser
                if(text == null){
                    if(this.lastTokenWasAFieldNameAndCurrentTokenIsANewEntity) {
                        text = this.lastFieldName;
                    } else {
                        text = "__anonymous__";
                    }
                }
                //end of workaround
                
                return text;
            } catch (IOException e) {
                throw new TreeReaderException(e);
            }
        }

        /**
         * Does nothing. Json does not have prefixes
         */
        @Override
        public String getPrefix() {
            return null;
        }

        @Override
        public String getFieldValue() throws TreeReaderException  {
            try {
                return parser.getText();
            } catch (IOException e) {
                throw new TreeReaderException(e);
            }
        }

        @Override
        public boolean hasNext() {
            return true; //FIXME fairly obtuse, is there a better way (advancing, then rewinding?)
        }

        @Override
        public Token next() throws TreeReaderException {
            JsonToken next;
            try {
                next = parser.nextToken();
            } catch (JsonParseException e) {
                throw new TreeReaderException(e);
            } catch (IOException e) {
                throw new TreeReaderException(e);
            }
            
            // TODO just return null here?
            if(next == null) {
                throw new TreeReaderException("No more Json Tokens in stream");
            }
            
            //The following is a workaround for inconsistent Jackson JsonParser
            if(next == JsonToken.FIELD_NAME){
                try {
                    this.thisTokenIsAFieldName = true;
                    this.lastFieldName = parser.getCurrentName();
                } catch (IOException e) {
                    //silent
                }
            }else if(next == JsonToken.START_ARRAY || next == JsonToken.START_OBJECT){
                if(this.thisTokenIsAFieldName){
                    this.lastTokenWasAFieldNameAndCurrentTokenIsANewEntity = true;
                    this.thisTokenIsAFieldName = false;
                }else{
                    this.lastTokenWasAFieldNameAndCurrentTokenIsANewEntity = false;
                    this.lastFieldName = null;
                }
            }else{
                this.lastTokenWasAFieldNameAndCurrentTokenIsANewEntity = false;
                this.lastFieldName = null;
                this.thisTokenIsAFieldName = false;
            }
            //end of workaround
                
            return mapToToken(next);
        }
        
        protected Token mapToToken(JsonToken token){
            switch(token){
                case START_ARRAY: return Token.StartEntity;
                case END_ARRAY: return Token.EndEntity;
                case START_OBJECT: return Token.StartEntity;
                case END_OBJECT: return Token.EndEntity;
                case VALUE_STRING: return Token.Value;
                case FIELD_NAME: return Token.Ignorable; //returned by the getLocalName function()
                case VALUE_NUMBER_INT: return Token.Value;
                //Json does not have START_DOCUMENT token type (so ignored as default)
                //Json does not have END_DOCUMENT token type (so ignored as default)
                case VALUE_TRUE : return Token.Value;
                case VALUE_NUMBER_FLOAT : return Token.Value;
                case VALUE_NULL : return Token.Value;
                case VALUE_FALSE : return Token.Value;
                case VALUE_EMBEDDED_OBJECT : return Token.Ignorable;
                case NOT_AVAILABLE : return Token.Ignorable;
                default: return Token.Ignorable;
            }
        }
    }
}