前言

深度优先遍历简称DFS，主要思路是从图中一个未访问的顶点 V 开始，沿着一条路一直走到底，然后从这条路尽头的节点回退到上一个节点，再从另一条路开始走到底，不断递归重复此过程，直到所有的顶点都遍历完成，它的特点是不撞南墙不回头，先走完一条路，再换一条路继续走。

使用递归实现深度优先遍历算法代码实现

public class DataFlowGraph {private static final String NODE_PROPERTY="nodeProperty";private static final String EDGE_LABLE="link";/*** 图*/private Graph graph =null;/*** 图遍历临时栈*/private Stack<String> stack = new Stack<String>();/*** 起点开始的所有路径*/private Map<String,List<List<String>>> allPathMap=new HashMap<>();public DataFlowGraph (String flow) {JSONObject jsonObj= JSONObject.parseObject(flow);generateGraph(jsonObj);}public FlowGraph(JSONObject flowJson) {generateGraph(flowJson);}/*** 遍历DAG图中所有路径* @param id* @throws Exception */public void findPathByStart(String id) throws Exception {stack.push(id);boolean bl=cyclicCheck(stack);if(bl) {throw new Exception("图存在环路");}Vertex vertex=graph.getVertex(id);Iterable<Vertex>  outVertexs=vertex.getVertices(Direction.OUT);int len=count(outVertexs);if(len>0) {          for(Vertex node:outVertexs) {findPathByStart(node.getId().toString());        }stack.pop();   }else {addToPath(stack);if(!stack.isEmpty()) {stack.pop();}return;}}/*** 检查是否存在环路 * @param pathStack* @return true 存在 false 不存在*/private boolean cyclicCheck(Stack<String> pathStack) {HashSet<String> set = new HashSet<>();set.addAll(pathStack);int setSize=set.size();int stackSize=pathStack.size();if(stackSize>setSize) {return true;}else {return false;}}/*** 将pathStack转换为list，* @param pathStack*/private void addToPath(Stack<String> pathStack) {List<String> singlePath=new ArrayList<String>();singlePath.addAll(pathStack);String startId=singlePath.get(0);List<List<String>> pathList=allPathMap.get(startId);if(pathList==null) {pathList=new ArrayList<List<String>>();allPathMap.put(startId, pathList);}pathList.add(singlePath);}/*** 根据节点id获取其属性* @param nodeId* @return*/public JSONObject getNode(String nodeId) {Vertex vertex=graph.getVertex(nodeId);if(vertex!=null) {return (JSONObject)vertex.getProperty(NODE_PROPERTY);}else {return null;}}/*** 获取下一步所有节点* @param nodeId* @return*/public JSONArray getNextNode(String nodeId) {JSONArray array=null;Iterable<Edge> ie=graph.getVertex(nodeId).getEdges(Direction.OUT);for(Edge edge:ie) {Vertex vertex=edge.getVertex(Direction.OUT);if(array==null) {array=new JSONArray();}array.add(vertex.getProperty(NODE_PROPERTY));}return array;}/*** 获取所有起始节点* @return*/public List<String> getStartNodes() {List<String> starts=new ArrayList<String>();Iterable<Vertex> iterator=graph.getVertices();for(Vertex tmpv:iterator) {Iterable<Edge> edges=tmpv.getEdges(Direction.IN, EDGE_LABLE);int count=count(edges);if(count==0) {starts.add(tmpv.getId().toString());}}return starts;}/*** 通过json串生成图* @param flowJson*/private void generateGraph(JSONObject flowJson) {graph = new TinkerGraph();//构建VertexJSONArray nodes=flowJson.getJSONArray("nodes");Map<String,Vertex> nodeMap=new HashMap<String,Vertex>();int len=nodes.size();for(int i=0;i<len;i++) {JSONObject node=nodes.getJSONObject(i);String id=node.getString("id");Vertex vertex = GraphHelper.addVertex(graph, id, NODE_PROPERTY, node);nodeMap.put(id, vertex);}//构建EdgeJSONArray links=flowJson.getJSONArray(JsonContant.DAG_LINKS);Map<String,JSONObject> linkMap=new HashMap<String,JSONObject>();len=links.size();for(int i=0;i<len;i++) {JSONObject link=links.getJSONObject(i);String id=link.getString(JsonContant.DAG_LINKS_ID);String fromId=link.getString(JsonContant.DAG_LINKS_FROM);String toId=link.getString(JsonContant.DAG_LINKS_TO);linkMap.put(id, link);Vertex vertexFrom=nodeMap.get(fromId);Vertex vertexTo=nodeMap.get(toId);GraphHelper.addEdge(graph,id, vertexFrom, vertexTo,"link" ,"name", "edge"+i);}}public List<List<String>> getAllPath(String startId) {return allPathMap.get(startId);} 
}