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co.cask.hydrator.plugin.XMLParser Maven / Gradle / Ivy
/*
* Copyright © 2016 Cask Data, 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 co.cask.hydrator.plugin;
import co.cask.cdap.api.annotation.Description;
import co.cask.cdap.api.annotation.Macro;
import co.cask.cdap.api.annotation.Name;
import co.cask.cdap.api.annotation.Plugin;
import co.cask.cdap.api.data.format.StructuredRecord;
import co.cask.cdap.api.data.schema.Schema;
import co.cask.cdap.api.plugin.PluginConfig;
import co.cask.cdap.etl.api.Emitter;
import co.cask.cdap.etl.api.InvalidEntry;
import co.cask.cdap.etl.api.PipelineConfigurer;
import co.cask.cdap.etl.api.Transform;
import co.cask.cdap.etl.api.TransformContext;
import com.google.common.base.Strings;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;
/**
* Parses XML Event using XPath.
* This should generally be used in conjunction with the XML Reader Batch Source.
*/
@Plugin(type = Transform.PLUGIN_TYPE)
@Name("XMLParser")
@Description("Parse XML events based on XPath")
public class XMLParser extends Transform {
private static final String EXIT_ON_ERROR = "Exit on error";
private static final String WRITE_ERROR_DATASET = "Write to error dataset";
private final Config config;
private Schema outSchema;
private Map xPathMapping = new HashMap<>();
// Required only for testing.
public XMLParser(Config config) {
this.config = config;
}
@Override
public void configurePipeline(PipelineConfigurer pipelineConfigurer) throws IllegalArgumentException {
super.configurePipeline(pipelineConfigurer);
outSchema = config.getOutputSchema();
validateXpathAndSchema();
pipelineConfigurer.getStageConfigurer().setOutputSchema(outSchema);
}
@Override
public void initialize(TransformContext context) throws Exception {
super.initialize(context);
outSchema = config.getOutputSchema();
xPathMapping = getXPathMapping();
}
/**
* Valid if xpathMappings and schema contain the same field names.
*/
private void validateXpathAndSchema() {
xPathMapping = getXPathMapping();
List outFields = outSchema.getFields();
// Checks if all the fields in the XPath mapping are present in the output schema.
// If they are not a list of fields that are not present is included in the error message.
StringBuilder notOutput = new StringBuilder();
for (Schema.Field field : outFields) {
String fieldName = field.getName();
if (!xPathMapping.keySet().contains(field.getName())) {
notOutput.append(fieldName + ";");
}
}
if (notOutput.length() > 0) {
throw new IllegalArgumentException("Following fields are not present in output schema :" +
notOutput.toString());
}
}
private Map getXPathMapping() {
Map map = new HashMap<>();
String[] xpaths = config.xPathFieldMapping.split(",");
for (String xpath : xpaths) {
String[] xpathmap = xpath.split(":"); //name:xpath[,name:xpath]*
String fieldName = xpathmap[0].trim();
if (Strings.isNullOrEmpty(fieldName)) {
throw new IllegalArgumentException("Field name cannot be null or empty.");
} else if (xpathmap.length < 2 || Strings.isNullOrEmpty(xpathmap[1])) {
throw new IllegalArgumentException(String.format("XPath for field name %s cannot be null or empty.",
fieldName));
}
map.put(fieldName, xpathmap[1].trim());
}
return map;
}
@Override
public void transform(StructuredRecord input, Emitter emitter) {
try {
InputSource source = new InputSource(new StringReader((String) input.get(config.inputField)));
source.setEncoding(config.encoding);
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = builderFactory.newDocumentBuilder();
Document document = documentBuilder.parse(source);
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
StructuredRecord.Builder builder = StructuredRecord.builder(outSchema);
for (Schema.Field field : outSchema.getFields()) {
String fieldName = field.getName();
//To evaluate a node, the type(Nodelist or Node) should be known before hand.
//Since, the type is not specified from user inputs, taking everything as NodeList and then evaluating.
NodeList nodeList = (NodeList) xpath.compile(xPathMapping.get(fieldName)).evaluate(document,
XPathConstants.NODESET);
if (nodeList.getLength() > 1) {
throw new IllegalArgumentException("Cannot specify an XPath that is an array");
}
Node node = nodeList.item(0);
//Since all columns have nullable schema extracting not nullable type.
Schema.Type type = field.getSchema().getNonNullable().getType();
String value = getValue(node, type, fieldName);
if (value == null) {
builder.set(fieldName, null);
} else {
builder.convertAndSet(fieldName, value);
}
}
emitter.emit(builder.build());
} catch (Exception e) {
switch (config.processOnError) {
case EXIT_ON_ERROR:
throw new IllegalStateException("Terminating process on error: " + e.getMessage(), e);
case WRITE_ERROR_DATASET:
emitter.emitError(new InvalidEntry<>(31, e.getStackTrace()[0].toString() + " : " + e.getMessage(), input));
break;
default:
//ignore on error(case "Ignore error and continue")
break;
}
}
}
/**
* Get the node value to be parsed into the required format by parseValues().
*
* @param node Node from which the text has to be extracted
* @param type schema type to check if it is a nullable string, in case the xpath evaluates to node with children
* @param fieldName field name for which the type is to be evaluated
* @return node value as string
*/
private String getValue(Node node, Schema.Type type, String fieldName) {
if (node != null) {
Node firstChild = node.getFirstChild();
//If the xpath evaluates to node which contains child element, the output will be an xml record
if (firstChild != null && (firstChild.getNodeType() == Node.ELEMENT_NODE || (firstChild.getNextSibling()
!= null && (firstChild.getNextSibling().getNodeType() == Node.ELEMENT_NODE)))) {
if (!type.equals(Schema.Type.STRING)) {
throw new IllegalArgumentException(String.format("The xpath returned node which contains child nodes. " +
"Cannot convert %s to type %s", fieldName, type));
} else {
return nodeToString(node.cloneNode(true));
}
} else {
return node.getTextContent();
}
} else {
return null;
}
}
/**
* Convert node to string to be returned in the output, for cases which contains child elements.
*
* @param node node to be converted to string
* @return converted node as string
*/
private String nodeToString(Node node) {
StringWriter stringWriter = new StringWriter();
try {
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.setOutputProperty(OutputKeys.INDENT, "no");
transformer.transform(new DOMSource(node), new StreamResult(stringWriter));
} catch (TransformerException e) {
throw new IllegalArgumentException("Cannot convert node to string. Transformer exception ", e);
}
return stringWriter.toString();
}
/**
* Configuration for the XMLParser transform..
*/
public static class Config extends PluginConfig {
@Name("input")
@Description("The field in the input record that is the source of the XML event or record.")
@Macro
private final String inputField;
@Description("The source XML character set encoding (default UTF-8).")
@Macro
private final String encoding;
@Name("xPathMappings")
@Description("Mapping of the field names to the XPaths of the XML record. A comma-separated list, each element " +
"of which is a field name, followed by a colon, followed by an XPath expression. XPath location paths can " +
"include predicates and supports XPath 1.0. Example : :")
private final String xPathFieldMapping;
@Description("Mapping of field names in the output schema to data types. Consists of a comma-separated list, " +
"each element of which is a field name followed by a colon and a type, where the field names are the same as " +
"used in the xPathMappings, and the type is one of: boolean, int, long, float, double, bytes, or string. " +
"Example : :")
private final String fieldTypeMapping;
@Description("The action to take in case of an error.\n" +
" - \"Ignore error and continue\"\n" +
" - \"Exit on error\" : Stops processing upon encountering an error\n" +
" - \"Write to error dataset\" : Writes the error record to an error dataset and continues")
private final String processOnError;
public Config(String inputField, String encoding, String xPathFieldMapping, String fieldTypeMapping,
String processOnError) {
this.inputField = inputField;
this.encoding = encoding;
this.xPathFieldMapping = xPathFieldMapping;
this.fieldTypeMapping = fieldTypeMapping;
this.processOnError = processOnError;
}
/**
* Create output schema from the field name and type value coming from keyvalue-dropdown widget.
* Since the xpath can evaluate to null(when no node is selected), creating nullable schema for all columns.
*
* @return output schema
*/
private Schema getOutputSchema() {
List fields = new ArrayList<>();
String[] mappings = fieldTypeMapping.split(",");
for (String mapping : mappings) {
String[] params = mapping.split(":");
String fieldName = params[0].trim();
if (Strings.isNullOrEmpty(fieldName)) {
throw new IllegalArgumentException("Field name cannot be null or empty.");
} else if (params.length < 2 || Strings.isNullOrEmpty(params[1])) {
throw new IllegalArgumentException("Type cannot be null. Please specify type for " + fieldName);
}
Schema.Field field = Schema.Field.of(fieldName, Schema.nullableOf(Schema.of(Schema.Type.valueOf(
params[1].trim().toUpperCase()))));
if (fields.contains(field)) {
throw new IllegalArgumentException(String.format("Field %s already has type specified. Duplicate field %s",
fieldName, fieldName));
} else {
fields.add(field);
}
}
return Schema.recordOf("record", fields);
}
}
}
