[INLONG-10905][SDK] Transform support Length() function (apache#10908)

inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/LengthFunction.java

@@ -0,0 +1,49 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.inlong.sdk.transform.process.function;
+
+import org.apache.inlong.sdk.transform.decode.SourceData;
+import org.apache.inlong.sdk.transform.process.Context;
+import org.apache.inlong.sdk.transform.process.operator.OperatorTools;
+import org.apache.inlong.sdk.transform.process.parser.ValueParser;
+
+import net.sf.jsqlparser.expression.Function;
+
+/**
+ * LengthFunction
+ * description: length(string)
+ * - return the length of the string
+ * - return NULL if the string is NULL
+ */
+public class LengthFunction implements ValueParser {
+
+    private final ValueParser stringParser;
+
+    public LengthFunction(Function expr) {
+        stringParser = OperatorTools.buildParser(expr.getParameters().getExpressions().get(0));
+    }
+
+    @Override
+    public Object parse(SourceData sourceData, int rowIndex, Context context) {
+        Object stringObject = stringParser.parse(sourceData, rowIndex, context);
+        if (stringObject == null) {
+            return null;
+        }
+        return OperatorTools.parseString(stringObject).length();
+    }
+}

inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/operator/OperatorTools.java

@@ -28,6 +28,7 @@
 import org.apache.inlong.sdk.transform.process.function.ExpFunction;
 import org.apache.inlong.sdk.transform.process.function.FloorFunction;
 import org.apache.inlong.sdk.transform.process.function.FromUnixTimeFunction;
+import org.apache.inlong.sdk.transform.process.function.LengthFunction;
 import org.apache.inlong.sdk.transform.process.function.LnFunction;
 import org.apache.inlong.sdk.transform.process.function.LocateFunction;
 import org.apache.inlong.sdk.transform.process.function.Log10Function;
@@ -144,6 +145,7 @@ public class OperatorTools {
         functionMap.put("unix_timestamp", UnixTimestampFunction::new);
         functionMap.put("to_timestamp", ToTimestampFunction::new);
         functionMap.put("to_base64", ToBase64Function::new);
+        functionMap.put("length", LengthFunction::new);
     }
 
     public static ExpressionOperator buildOperator(Expression expr) {

inlong-sdk/transform-sdk/src/test/java/org/apache/inlong/sdk/transform/process/TestTransformStringFunctionsProcessor.java

@@ -200,4 +200,27 @@ public void testToBase64Function() throws Exception {
         Assert.assertEquals(1, output2.size());
         Assert.assertEquals(output2.get(0), "result=aGVsbG8gd29ybGQ=");
     }
+
+    @Test
+    public void testLengthFunction() throws Exception {
+        String transformSql = "select length(string1) from source";
+        TransformConfig config = new TransformConfig(transformSql);
+        TransformProcessor<String, String> processor1 = TransformProcessor
+                .create(config, SourceDecoderFactory.createCsvDecoder(csvSource),
+                        SinkEncoderFactory.createKvEncoder(kvSink));
+        // case1: length('hello world')
+        List<String> output1 = processor1.transform("hello world|apple|cloud|2|1|3", new HashMap<>());
+        Assert.assertEquals(1, output1.size());
+        Assert.assertEquals("result=11", output1.get(0));
+
+        transformSql = "select length(xxd) from source";
+        config = new TransformConfig(transformSql);
+        processor1 = TransformProcessor
+                .create(config, SourceDecoderFactory.createCsvDecoder(csvSource),
+                        SinkEncoderFactory.createKvEncoder(kvSink));
+        // case2: length(null)
+        output1 = processor1.transform("hello world|apple|cloud|2|1|3", new HashMap<>());
+        Assert.assertEquals(1, output1.size());
+        Assert.assertEquals("result=null", output1.get(0));
+    }
 }