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net.javacrumbs.json2xml.JsonSaxAdapter Maven / Gradle / Ivy
/*
* Copyright 2011 the original author or authors.
*
* 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 net.javacrumbs.json2xml;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;
import java.io.IOException;
import static com.fasterxml.jackson.core.JsonToken.END_ARRAY;
import static com.fasterxml.jackson.core.JsonToken.END_OBJECT;
import static com.fasterxml.jackson.core.JsonToken.FIELD_NAME;
import static com.fasterxml.jackson.core.JsonToken.START_ARRAY;
import static com.fasterxml.jackson.core.JsonToken.START_OBJECT;
import static com.fasterxml.jackson.core.JsonToken.VALUE_NULL;
/**
* Converts JSON to SAX events. It can be used either directly
*
*
* ContentHandler ch = ...;
* JsonSaxAdapter adapter = new JsonSaxAdapter(JsonSaxAdapterTest.JSON, ch);
* adapter.parse();
*
*
*
* or using {@link JsonXmlReader}
*
*
* Transformer transformer = TransformerFactory.newInstance().newTransformer();
* InputSource source = new InputSource(...);
* Result result = ...;
* transformer.transform(new SAXSource(new JsonXmlReader(),source), result);
*
*
*/
public class JsonSaxAdapter {
private static final AttributesImpl EMPTY_ATTRIBUTES = new AttributesImpl();
private final JsonParser jsonParser;
private final ContentHandler contentHandler;
private final String namespaceUri;
private final boolean addTypeAttributes;
private final String artificialRootName;
private final ElementNameConverter nameConverter;
private static final JsonFactory JSON_FACTORY = new JsonFactory();
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param json JSON to parse
* @param contentHandler target of SAX events
*/
public JsonSaxAdapter(final String json, final ContentHandler contentHandler) {
this(parseJson(json), contentHandler);
}
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param jsonParser parsed JSON
* @param contentHandler target of SAX events
*/
public JsonSaxAdapter(final JsonParser jsonParser, final ContentHandler contentHandler) {
this(jsonParser, contentHandler, "");
}
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param jsonParser parsed JSON
* @param contentHandler target of SAX events
* @param namespaceUri namespace of the generated XML
*/
public JsonSaxAdapter(final JsonParser jsonParser, final ContentHandler contentHandler, final String namespaceUri) {
this(jsonParser, contentHandler, namespaceUri, false);
}
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param jsonParser parsed JSON
* @param contentHandler target of SAX events
* @param namespaceUri namespace of the generated XML
* @param addTypeAttributes adds type information as attributes
*/
public JsonSaxAdapter(final JsonParser jsonParser, final ContentHandler contentHandler, final String namespaceUri, final boolean addTypeAttributes) {
this(jsonParser, contentHandler, namespaceUri, addTypeAttributes, null);
}
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param jsonParser parsed JSON
* @param contentHandler target of SAX events
* @param namespaceUri namespace of the generated XML
* @param addTypeAttributes adds type information as attributes
* @param artificialRootName if set, an artificial root is generated so JSON documents with more roots can be handeled.
*/
public JsonSaxAdapter(final JsonParser jsonParser, final ContentHandler contentHandler, final String namespaceUri,
final boolean addTypeAttributes, final String artificialRootName) {
this(jsonParser, contentHandler, namespaceUri, addTypeAttributes, artificialRootName, null);
}
/**
* Creates JsonSaxAdapter that coverts JSON to SAX events.
* @param jsonParser parsed JSON
* @param contentHandler target of SAX events
* @param namespaceUri namespace of the generated XML
* @param addTypeAttributes adds type information as attributes
* @param artificialRootName if set, an artificial root is generated so JSON documents with more roots can be handeled.
*/
public JsonSaxAdapter(final JsonParser jsonParser, final ContentHandler contentHandler, final String namespaceUri,
final boolean addTypeAttributes, final String artificialRootName, final ElementNameConverter nameConverter) {
this.jsonParser = jsonParser;
this.contentHandler = contentHandler;
this.namespaceUri = namespaceUri;
this.addTypeAttributes = addTypeAttributes;
this.artificialRootName = artificialRootName;
this.nameConverter = nameConverter;
contentHandler.setDocumentLocator(new DocumentLocator());
}
private static JsonParser parseJson(final String json) {
try {
return JSON_FACTORY.createParser(json);
} catch (Exception e) {
throw new ParserException("Parsing error", e);
}
}
/**
* Method parses JSON and emits SAX events.
*/
public void parse() throws ParserException {
try {
jsonParser.nextToken();
contentHandler.startDocument();
if (shouldAddArtificialRoot()) {
startElement(artificialRootName);
parseElement(artificialRootName, false);
endElement(artificialRootName);
} else if (START_OBJECT.equals(jsonParser.getCurrentToken())) {
int elementsWritten = parseObject();
if (elementsWritten>1) {
throw new ParserException("More than one root element. Can not generate legal XML. You can set artificialRootName to generate an artificial root.");
}
} else {
throw new ParserException("Unsupported root element. Can not generate legal XML. You can set artificialRootName to generate an artificial root.");
}
contentHandler.endDocument();
} catch (Exception e) {
throw new ParserException("Parsing error: " + e.getMessage(), e);
}
}
private boolean shouldAddArtificialRoot() {
return artificialRootName != null && artificialRootName.length() > 0;
}
/**
* Parses generic object.
*
* @return number of elements written
* @throws IOException
* @throws JsonParseException
* @throws Exception
*/
private int parseObject() throws Exception {
int elementsWritten = 0;
while (jsonParser.nextToken() != null && jsonParser.getCurrentToken() != END_OBJECT) {
if (FIELD_NAME.equals(jsonParser.getCurrentToken())) {
String elementName = convertName(jsonParser.getCurrentName());
//jump to element value
jsonParser.nextToken();
startElement(elementName);
parseElement(elementName, false);
endElement(elementName);
elementsWritten++;
} else {
throw new ParserException("Error when parsing. Expected field name got " + jsonParser.getCurrentToken());
}
}
return elementsWritten;
}
private String convertName(String name) {
if (nameConverter != null) {
return nameConverter.convertName(name);
} else {
return name;
}
}
/**
* Pares JSON element.
* @param elementName
* @param inArray if the element is in an array
* @throws Exception
*/
private void parseElement(final String elementName, final boolean inArray) throws Exception {
JsonToken currentToken = jsonParser.getCurrentToken();
if (START_OBJECT.equals(currentToken)) {
parseObject();
} else if (START_ARRAY.equals(currentToken)) {
if (inArray) {
startElement(elementName);
parseArray(elementName);
endElement(elementName);
} else {
parseArray(elementName);
}
} else if (currentToken.isScalarValue()) {
if (inArray) {
startElement(elementName);
parseValue();
endElement(elementName);
} else {
parseValue();
}
}
}
private void parseArray(final String elementName) throws Exception {
while (jsonParser.nextToken() != END_ARRAY && jsonParser.getCurrentToken() != null) {
parseElement(elementName, true);
}
}
private void parseValue() throws Exception {
if (VALUE_NULL != jsonParser.getCurrentToken()) {
String text = jsonParser.getText();
contentHandler.characters(text.toCharArray(), 0, text.length());
}
}
private void startElement(final String elementName) throws SAXException {
contentHandler.startElement(namespaceUri, elementName, elementName, getTypeAttributes());
}
protected Attributes getTypeAttributes() {
if (addTypeAttributes) {
String currentTokenType = getCurrentTokenType();
if (currentTokenType != null) {
AttributesImpl attributes = new AttributesImpl();
attributes.addAttribute("", "type", "type", "string", currentTokenType);
return attributes;
} else {
return EMPTY_ATTRIBUTES;
}
} else {
return EMPTY_ATTRIBUTES;
}
}
protected String getCurrentTokenType() {
switch (jsonParser.getCurrentToken()) {
case VALUE_NUMBER_INT:
return "int";
case VALUE_NUMBER_FLOAT:
return "float";
case VALUE_FALSE:
return "boolean";
case VALUE_TRUE:
return "boolean";
case VALUE_STRING:
return "string";
case VALUE_NULL:
return "null";
case START_ARRAY:
return "array";
default:
return null;
}
}
private void endElement(final String elementName) throws SAXException {
contentHandler.endElement(namespaceUri, elementName, elementName);
}
public static class ParserException extends RuntimeException {
private static final long serialVersionUID = 2194022343599245018L;
public ParserException(final String message, final Throwable cause) {
super(message, cause);
}
public ParserException(final String message) {
super(message);
}
public ParserException(final Throwable cause) {
super(cause);
}
}
private class DocumentLocator implements Locator {
public String getPublicId() {
Object sourceRef = jsonParser.getCurrentLocation().getSourceRef();
if (sourceRef != null) {
return sourceRef.toString();
} else {
return "";
}
}
public String getSystemId() {
return getPublicId();
}
public int getLineNumber() {
return jsonParser.getCurrentLocation() != null ? jsonParser.getCurrentLocation().getLineNr() : -1;
}
public int getColumnNumber() {
return jsonParser.getCurrentLocation() != null ? jsonParser.getCurrentLocation().getColumnNr() : -1;
}
}
}
