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JsoupHtmlTextExtractor.java
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/
JsoupHtmlTextExtractor.java
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/****************************************************************
O * Licensed to the Apache Software Foundation (ASF) under one *
* or more contributor license agreements. See the NOTICE file *
* distributed with this work for additional information *
* regarding copyright ownership. The ASF licenses this file *
* to you 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 org.apache.james.jmap.utils;
import java.util.Optional;
import java.util.stream.Stream;
import org.apache.commons.lang.StringUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.Node;
import org.jsoup.nodes.TextNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class JsoupHtmlTextExtractor implements HtmlTextExtractor {
private static final Logger LOGGER = LoggerFactory.getLogger(JsoupHtmlTextExtractor.class);
public static final String BR_TAG = "br";
public static final String UL_TAG = "ul";
public static final String OL_TAG = "ol";
public static final String LI_TAG = "li";
public static final String P_TAG = "p";
public static final String IMG_TAG = "img";
public static final String ALT_TAG = "alt";
public static final int INITIAL_LIST_NESTED_LEVEL = 0;
@Override
public String toPlainText(String html) {
try {
Document document = Jsoup.parse(html);
Element body = Optional.ofNullable(document.body()).orElse(document);
return flatten(body, INITIAL_LIST_NESTED_LEVEL)
.map(this::convertNodeToText)
.reduce("", (s1, s2) -> s1 + s2);
} catch (Exception e) {
LOGGER.warn("Failed extracting text from html", e);
return html;
}
}
private String convertNodeToText(HTMLNode htmlNode) {
Node node = htmlNode.underlyingNode;
if (node instanceof TextNode) {
TextNode textNode = (TextNode) node;
return textNode.getWholeText();
}
if (node instanceof Element) {
Element element = (Element) node;
if (element.tagName().equals(BR_TAG)) {
return "\n";
}
if (isList(element)) {
return convertListElement(htmlNode.listNestedLevel);
}
if (element.tagName().equals(OL_TAG)) {
return "\n\n";
}
if (element.tagName().equals(LI_TAG)) {
return "\n" + StringUtils.repeat(" ", htmlNode.listNestedLevel) + "- ";
}
if (element.tagName().equals(P_TAG)) {
return "\n\n";
}
if (element.tagName().equals(IMG_TAG)) {
return "[" + element.attributes().get(ALT_TAG) + "]";
}
}
return "";
}
private String convertListElement(int nestedLevel) {
if (nestedLevel == 0) {
return "\n\n";
} else {
return "";
}
}
Stream<HTMLNode> flatten(Node base, int listNestedLevel) {
Position position = getPosition(base);
int nextElementLevel = getNewNestedLevel(listNestedLevel, base);
Stream<HTMLNode> baseStream = Stream.of(new HTMLNode(base, listNestedLevel));
Stream<HTMLNode> flatChildren = base.childNodes()
.stream()
.flatMap(node -> flatten(node, nextElementLevel));
switch (position) {
case PREFIX:
return Stream.concat(baseStream, flatChildren);
case SUFFIX:
return Stream.concat(flatChildren, baseStream);
default:
throw new RuntimeException("Unexpected POSITION for node element: " + position);
}
}
private int getNewNestedLevel(int listNestedLevel, Node node) {
if (node instanceof Element) {
Element element = (Element) node;
if (isList(element)) {
return listNestedLevel + 1;
}
}
return listNestedLevel;
}
private boolean isList(Element element) {
return element.tagName().equals(UL_TAG) || element.tagName().equals(OL_TAG);
}
private enum Position {
PREFIX,
SUFFIX
}
private Position getPosition(Node node) {
if (node instanceof Element) {
Element element = (Element) node;
if (element.tagName().equals(LI_TAG)) {
return Position.PREFIX;
}
}
return Position.SUFFIX;
}
private static class HTMLNode {
private final Node underlyingNode;
private final int listNestedLevel;
public HTMLNode(Node underlyingNode, int listNestedLevel) {
this.underlyingNode = underlyingNode;
this.listNestedLevel = listNestedLevel;
}
}
}