崩溃…… 我刚开始接触neo4j数据库，是一个小白，找了一个GitHub上面应该相对成熟的代码程序进行学习。 web项目可以运行，且不报错，在运行出的web页面中有一个查询按钮是通过调用servlet来获取neo4J中的数据，以达到在页面中可视化的结果，然而在我点击查询按钮后没有出现结果，在控制台中报出了servlet调用异常的报错信息，说是没有在neo4j中获取有效的数据。 运行环境：idea2019.3 + tomcat7 + java11 连接neo4j和项目的驱动使用的neo4j.java.driver.1.4.4. 报错信息如下：

严重: 在路径为[/abc]的上下文中，servlet[DisplayController]的Servlet.service()引发异常
org.neo4j.driver.v1.exceptions.ServiceUnavailableException: Failed to receive any data from the connected address localhost:7687. Please ensure a working connection to the database.
	at org.neo4j.driver.internal.security.TLSSocketChannel.channelRead(TLSSocketChannel.java:176)
	at org.neo4j.driver.internal.security.TLSSocketChannel.unwrap(TLSSocketChannel.java:235)
	at org.neo4j.driver.internal.security.TLSSocketChannel.runHandshake(TLSSocketChannel.java:137)
	at org.neo4j.driver.internal.security.TLSSocketChannel.create(TLSSocketChannel.java:85)
	at org.neo4j.driver.internal.security.TLSSocketChannel.create(TLSSocketChannel.java:75)
	at org.neo4j.driver.internal.net.ChannelFactory.create(ChannelFactory.java:49)
	at org.neo4j.driver.internal.net.SocketClient.start(SocketClient.java:126)
	at org.neo4j.driver.internal.net.SocketConnection.startSocketClient(SocketConnection.java:92)
	at org.neo4j.driver.internal.net.SocketConnection.<init>(SocketConnection.java:67)
	at org.neo4j.driver.internal.net.SocketConnector.createConnection(SocketConnector.java:77)
	at org.neo4j.driver.internal.net.SocketConnector.connect(SocketConnector.java:50)
	at org.neo4j.driver.internal.net.pooling.SocketConnectionPool$ConnectionSupplier.get(SocketConnectionPool.java:216)
	at org.neo4j.driver.internal.net.pooling.SocketConnectionPool$ConnectionSupplier.get(SocketConnectionPool.java:198)
	at org.neo4j.driver.internal.net.pooling.BlockingPooledConnectionQueue.acquire(BlockingPooledConnectionQueue.java:96)
	at org.neo4j.driver.internal.net.pooling.SocketConnectionPool.acquireConnection(SocketConnectionPool.java:149)
	at org.neo4j.driver.internal.net.pooling.SocketConnectionPool.acquire(SocketConnectionPool.java:76)
	at org.neo4j.driver.internal.DirectConnectionProvider.acquireConnection(DirectConnectionProvider.java:47)
	at org.neo4j.driver.internal.DirectConnectionProvider.verifyConnectivity(DirectConnectionProvider.java:67)
	at org.neo4j.driver.internal.DirectConnectionProvider.<init>(DirectConnectionProvider.java:41)
	at org.neo4j.driver.internal.DriverFactory.createDirectDriver(DriverFactory.java:109)
	at org.neo4j.driver.internal.DriverFactory.createDriver(DriverFactory.java:93)
	at org.neo4j.driver.internal.DriverFactory.newInstance(DriverFactory.java:67)
	at org.neo4j.driver.v1.GraphDatabase.driver(GraphDatabase.java:135)
	at org.neo4j.driver.v1.GraphDatabase.driver(GraphDatabase.java:117)
	at org.neo4j.driver.v1.GraphDatabase.driver(GraphDatabase.java:92)
	at com.shuhan.Neo4jRestAPI.getDriver(Neo4jRestAPI.java:19)
	at com.shuhan.Neo4jRestAPI.executeFindRelationCypher(Neo4jRestAPI.java:95)
	at com.shuhan.model2.RelationshipBeanDBA.lookInto(RelationshipBeanDBA.java:125)
	at com.shuhan.controller.DisplayController.doGet(DisplayController.java:53)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:492)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:165)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1201)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:654)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:317)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:834) \n```



报错信息中涉及到的Displaycontroler代码段如下：

```js\n import com.shuhan.model2.RelationshipBeanDBA;
import systemInfo.SystemInfo;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

[@WebServlet](/user/WebServlet)(name = "DisplayController")
public class DisplayController extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //这句话可以解决从jsp页面接受到中文乱码问题
        request.setCharacterEncoding("utf-8");

        response.setContentType("text/html; charset=utf-8");

        PrintWriter out  = response.getWriter();

        String selectItem1 = request.getParameter("selectItem1");
        String selectItem2 = request.getParameter("selectItem2");
        String keyword = request.getParameter("keyword");
        String times = request.getParameter("times");//判断这次操作是用户点击查询按钮还是双击节点
        String isHide = request.getParameter("isHide");

        String nodeType = "";
        String nodeName = "";

        if(selectItem1!=null&&selectItem1!=""){
            if(selectItem2!=null&&selectItem2!=""){
                nodeType = selectItem2;
            }
            else nodeType= selectItem1;
        }
        nodeName  = keyword;

        String json = "";
        RelationshipBeanDBA relationshipBeanDBA = new RelationshipBeanDBA();
        //用户点击的是查询按钮！
        if(times.equals("first")||isHide.equals("yes")){
            json = relationshipBeanDBA.lookInto(nodeType,nodeName);
        }
        //用户双击了节点！
        else{
            //执行新的查询方法（允许多条查询语句语句同时进行）
            //先将语句加入到SystemInfo中，然后在得到全部的查询语句
            String cypher = "";

            StringBuffer stringBuffer = new StringBuffer("");
            stringBuffer.append("match p=(:");
            stringBuffer.append(nodeType);
            stringBuffer.append("{");
            stringBuffer.append("名称:");
            stringBuffer.append("\"");
            stringBuffer.append(nodeName);
            stringBuffer.append("\"");
            stringBuffer.append("}");
            stringBuffer.append(")");
            stringBuffer.append("-[*..1]-() return p");

            cypher = stringBuffer.toString();

            SystemInfo.addCypher(cypher);

            //得到所有的查询语句
            ArrayList<String> cypherArrayList = SystemInfo.getCypherArrayList();

            /*for(int i = 0;i<cypherArrayList.size();i++){
                System.out.println(cypherArrayList.get(i));
            }*/

            json = relationshipBeanDBA.lookIntos(cypherArrayList);
        }
        out.write(json);
    }
} \n```