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| <main role="main" class="ml-sm-auto px-4 w-100 h-100"> |
| <div class="sect1"> |
| <h2 id="about_plc4j">About PLC4J</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p><code>PLC4J</code> is a sub-project of <code>PLC4X</code> with implementations based on <code>Java</code> targeted at runtimes for <code>Java 1.8</code> or above.</p> |
| </div> |
| <div class="paragraph"> |
| <p>One of PLC4X’s core principals is, that an application using PLC4X should be independent of the PLC or protocol being used.</p> |
| </div> |
| <div class="paragraph"> |
| <p>When addressing a resource on a remote there are two parts that are dependent on the protocol and the type of PLC:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p>Addressing the PLC itself</p> |
| </li> |
| <li> |
| <p>Addressing a resource on the PLC</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>Providing this independence to addressing the PLC itself is completely handled by the <code>PlcDriverManager</code> the application requests a connection from.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Hereby the design of the <code>url string</code> passed to the <code>getConnection</code> method is greatly inspired by <code>JDBC</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The protocol prefix of the url specifies the type of driver being used.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example, when connecting to a Siemens PLC using the S7/Step7 Protocol, the url: <code>s7://192.42.0.98/1/2</code> causes the driver manager to create a S7 connection instance. |
| The part behind the <code>:</code> is hereby used by the driver implementation to configure that particular connection.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For a S7 connection, for example, this is <code>IP address/host name</code>/<code>rack number</code>/<code>slot number</code>. For different types of connections this url structure will greatly differ.</p> |
| </div> |
| <div class="paragraph"> |
| <p>As mentioned above, the second platform dependent information is the address of resources on a PLC. |
| The format of an address greatly depends on the type of connection. Therefore <code>parseAddress</code> is one of the only methods defined in the <code>PlcConnection</code> interface any connection has to implement.</p> |
| </div> |
| <div class="paragraph"> |
| <p>This method returns an object implementing the <code>Address</code> interface which then can be used by the same connection to identify remote resources.</p> |
| </div> |
| <div class="imageblock"> |
| <div class="content"> |
| <img src="../images/plc4x-architecture.png" alt="plc4x architecture" width="1000" height="574"/> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="usage">Usage</h3> |
| <div class="paragraph"> |
| <p>Below code example connects to a remote Siemens S7 PLC using the S7/Step7 protocol and then reads the state of the <code>inputs</code> and <code>outputs</code> from this.</p> |
| </div> |
| <div class="paragraph"> |
| <p>It also demonstrates two ways this information can be accessed:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p>Synchronously (The application pauses, till the response is received)</p> |
| </li> |
| <li> |
| <p>Asynchronously (The application continues and can</p> |
| </li> |
| </ul> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="java">package org.apache.plc4x.java.examples.helloplc4x; |
| |
| import org.apache.plc4x.java.PlcDriverManager; |
| import org.apache.plc4x.java.api.PlcConnection; |
| import org.apache.plc4x.java.api.exceptions.PlcRuntimeException; |
| import org.apache.plc4x.java.api.messages.PlcReadRequest; |
| import org.apache.plc4x.java.api.messages.PlcReadResponse; |
| import org.apache.plc4x.java.api.types.PlcResponseCode; |
| import org.apache.plc4x.java.api.value.PlcValue; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.util.concurrent.CompletionStage; |
| import java.util.concurrent.TimeUnit; |
| |
| public class HelloPlc4x { |
| |
| private static final Logger logger = LoggerFactory.getLogger(HelloPlc4x.class); |
| |
| /** |
| * Example code do demonstrate using PLC4X. |
| * |
| * @param args ignored. |
| */ |
| public static void main(String[] args) throws Exception { |
| CliOptions options = CliOptions.fromArgs(args); |
| if (options == null) { |
| CliOptions.printHelp(); |
| // Could not parse. |
| System.exit(1); |
| } |
| |
| // Establish a connection to the plc using the url provided as first argument |
| try (PlcConnection plcConnection = new PlcDriverManager().getConnection(options.getConnectionString())) { |
| |
| // Check if this connection support reading of data. |
| if (!plcConnection.getMetadata().canRead()) { |
| logger.error("This connection doesn't support reading."); |
| return; |
| } |
| |
| // Create a new read request: |
| // - Give the single item requested the alias name "value" |
| PlcReadRequest.Builder builder = plcConnection.readRequestBuilder(); |
| for (int i = 0; i < options.getFieldAddress().length; i++) { |
| builder.addItem("value-" + options.getFieldAddress()[i], options.getFieldAddress()[i]); |
| } |
| PlcReadRequest readRequest = builder.build(); |
| |
| ////////////////////////////////////////////////////////// |
| // Read synchronously ... |
| // NOTICE: the ".get()" immediately lets this thread pause until |
| // the response is processed and available. |
| logger.info("Synchronous request ..."); |
| PlcReadResponse syncResponse = readRequest.execute().get(); |
| // Simply iterating over the field names returned in the response. |
| printResponse(syncResponse); |
| |
| /*PlcValue asPlcValue = syncResponse.getAsPlcValue(); |
| System.out.println(asPlcValue.toString());*/ |
| |
| ////////////////////////////////////////////////////////// |
| // Read asynchronously ... |
| // Register a callback executed as soon as a response arrives. |
| /*logger.info("Asynchronous request ..."); |
| CompletionStage<? extends PlcReadResponse> asyncResponse = readRequest.execute(); |
| asyncResponse.whenComplete((readResponse, throwable) -> { |
| if (readResponse != null) { |
| printResponse(readResponse); |
| } else { |
| logger.error("An error occurred: " + throwable.getMessage(), throwable); |
| } |
| });*/ |
| |
| // Give the async request a little time... |
| TimeUnit.MILLISECONDS.sleep(1000); |
| plcConnection.close(); |
| System.exit(0); |
| } |
| } |
| |
| private static void printResponse(PlcReadResponse response) { |
| for (String fieldName : response.getFieldNames()) { |
| if (response.getResponseCode(fieldName) == PlcResponseCode.OK) { |
| int numValues = response.getNumberOfValues(fieldName); |
| // If it's just one element, output just one single line. |
| if (numValues == 1) { |
| logger.info("Value[{}]: {}", fieldName, response.getObject(fieldName)); |
| } |
| // If it's more than one element, output each in a single row. |
| else { |
| logger.info("Value[{}]:", fieldName); |
| for (int i = 0; i < numValues; i++) { |
| logger.info(" - {}", response.getObject(fieldName, i)); |
| } |
| } |
| } |
| // Something went wrong, to output an error message instead. |
| else { |
| logger.error("Error[{}]: {}", fieldName, response.getResponseCode(fieldName).name()); |
| } |
| } |
| } |
| |
| }</code></pre> |
| </div> |
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