The value of the project attribute is null

问题描述

导入Maven项目后,无法进行Update Maven project操作,报错信息如下:

The value of the project attribute is null  webSocket       line 1  Maven Java EE Configuration Problem

解决办法

可以尝试以下解决办法:

  • 首先,找到对应项目所在的文件目录,将.settings以及.project文件删除;
  • 然后,删除Eclipse中的对应项目(注意:不要把删除本地文件的勾勾上);
  • 最后,重新导入项目,并对项目进行更新操作。
### OPC UA Binary Schema Library and Specification in Java For working with the OPC UA Binary Schema within a Java environment, developers can utilize libraries that provide comprehensive support for this protocol. One of the most widely recognized solutions is the Eclipse Milo project which offers both server and client SDKs specifically designed for interacting with OPC UA services. Eclipse Milo supports various aspects of OPC UA including binary encoding as specified by the standard[^1]. This library allows applications written in Java to encode and decode data structures according to the OPC UA Binary schema efficiently while maintaining compliance with official specifications. To demonstrate how one might interact with these features using Eclipse Milo: ```java import org.eclipse.milo.opcua.sdk.client.OpcUaClient; import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue; public class OpcUaDataAccess { public static void main(String[] args) throws Exception { // Create an instance of OpcUaClient configured appropriately. final OpcUaClient client = ... ; // Connect to the server asynchronously. CompletableFuture<OpcUaClient> connectFuture = client.connect(); DataValue value = null; try (OpcUaClient connectedClient = connectFuture.get()) { Node node = connectedClient.getAddressSpace().getNode("ns=2;s=SomeVariable"); ReadValueId readValueId = new ReadValueId(node.getNodeId(), AttributeId.Value.uid(), null, QualifiedName.NULL_VALUE); UaResponseHeader header = connectedClient.readValue(0.0, TimestampsToReturn.Neither, Arrays.asList(readValueId)).get(); List<DataValue> values = ((ReadResponse)header).getResults(); if (!values.isEmpty()) { value = values.get(0); } } System.out.println(value.getValue()); } } ``` This code snippet illustrates establishing a connection between a Java application and an OPC UA compliant device over TCP/IP transport layer utilizing binary-encoded messages defined under OPC UA standards.
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