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    • net.minidev.json.actions.navigate.TreeNavigator Maven / Gradle / Ivy

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    JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.

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    package net.minidev.json.actions.navigate;

import net.minidev.json.JSONObject;
import net.minidev.json.actions.path.DotDelimiter;
import net.minidev.json.actions.path.TreePath;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

/**
 * Navigates only the branches of a {@link JSONObject} corresponding to the paths specified.
 * 
    
 * For each specified path to navigate, the {@link TreeNavigator} only traverses the matching
 * branch.
 * 
    
 * The navigator accepts an action and provides callback hooks for it to act on the traversed
 * nodes at each significant step. See {@link NavigateAction}.
 * 
    
 * See package-info for more details
 * 
    
 * Example:
 * 
    
 * To navigate the branch k1.k2 of the object {"k1":{"k2":"v1"}, "k3":{"k4":"v2"}} instantiate
 * the navigator like so: new JSONNavigator("k1.k2")
 *
 * @author [email protected]
 * @since 15 June 2016.
 *
 */
public class TreeNavigator, L extends List> {
	protected List pathsToNavigate;
	protected NavigateAction action;
	protected String pathPrefix = "";

	public TreeNavigator(NavigateAction action, List pathsToNavigate) {
		if (action == null) {
			throw new IllegalArgumentException("NavigateAction cannot be null");
		}
		this.action = action;
		this.pathsToNavigate = pathsToNavigate;
	}

	public TreeNavigator with(String pathPrefix) {
		this.pathPrefix = pathPrefix;
		return this;
	}

	public TreeNavigator(NavigateAction action, String... pathsToNavigate) {
		this(action, Arrays.asList(pathsToNavigate));
	}

	public void nav(M object) throws Exception {
		if (action.start(object, pathsToNavigate)) {
			for (String path : pathsToNavigate) {
				try {
					if (path != null && !path.equals("") && action.pathStart(path)) {
						TreePath jp = new TreePath(path, new DotDelimiter().withAcceptDelimiterInNodeName(true));
						nav(jp, object);
						action.pathEnd(path);
					}
				} catch (Exception e) {
					if (action.failSilently(path, e)) {
						break;
					} else if (action.failFast(path, e)) {
						throw e;
					}
				}
			}
		}
		action.end();
	}

	@SuppressWarnings("unchecked")
	public void nav(TreePath jp, M map) {
		if (map == null || !action.recurInto(jp, map)) {
			//source is null - navigation impossible
			return;
		}

		if (jp.hasNext()) {
			String key = jp.next();
			if (!map.containsKey(key)) {
				// cannot find next element of path in the source -
				// the specified path does not exist in the source
				action.pathTailNotFound(jp, map);
			} else if (map.get(key) instanceof Map) {
				//reached Map type node - handle it and recur into it
				nav(jp, (M) map.get(key));
			} else if (map.get(key) instanceof List) {
				//reached List type node - handle it and recur into it
				nav(jp, (L) map.get(key));
			} else if (jp.hasNext()) {
				// reached leaf node (not a container) in source but specified path expects children -
				// the specified path is illegal because it does not exist in the source.
				action.foundLeafBeforePathEnd(jp, map.get(key));
			} else if (!jp.hasNext()) {
				//reached leaf in source and specified path is also at leaf -> handle it
				action.handleLeaf(jp, map.get(key));
			} else {
				throw new IllegalStateException("fatal: unreachable code reached at '" + jp.origin() + "'");
			}
		}
		action.recurEnd(jp, (M) map);
	}

	@SuppressWarnings("unchecked")
	public void nav(TreePath jp, L list) {
		if (list == null || !action.recurInto(jp, (L) list)) {
			//list is null - navigation impossible
			return;
		}
		int arrIndex = 0;
		for (Object arrItem : list.toArray()) {
			if (arrItem instanceof Map) {
				// clone the path so that for each object in the array,
				// the iterator continues from the same position in the path
				TreePath jpClone = getClone(jp);
				nav(jpClone, (M) arrItem);
			} else if (arrItem instanceof List) {
				nav(jp, (L) arrItem);
			} else if (!jp.hasNext()) {
				//reached leaf - handle it
				action.handleLeaf(jp, arrIndex, arrItem);
			}
			arrIndex++;
		}
		action.recurEnd(jp, (L) list);
	}

	private TreePath getClone(TreePath jp) {
		try {
			return jp.clone();
		} catch (CloneNotSupportedException e) {
			throw new RuntimeException("failed to clone path", e);
		}
	}
}
    
    
    
    

    




    
    
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