请问一下，flink sql udf 通过字符串这样传进来，大家有没有一个好的实现办法呀？

从你的描述来看，你正在尝试使用Groovy编译器将一个字符串编译成一个类，然后将这个类的实例注册为Flink SQL的UDF。然而，你遇到了一个问题，那就是这个方法会抛出一个异常。

这个问题可能是由于Groovy编译器在编译字符串时遇到了问题，或者是由于Flink SQL的UDF注册过程中出现了问题。以下是一些可能的解决方案：

1. 检查Groovy编译器的输出：你可以查看Groovy编译器的输出，看看是否有任何错误消息。这可能会帮助你了解为什么编译失败。

2. 使用Java编译器：如果Groovy编译器不起作用，你可以尝试使用Java编译器。你可以使用Java的Compiler类来编译你的字符串。

3. 检查UDF的实现：你需要确保你的UDF实现了Flink SQL的UDF接口，并且它的签名符合Flink SQL的要求。

4. 检查UDF的注册：你需要确保你在注册UDF时使用的方法是正确的。你可以参考Flink的文档，看看如何正确地注册UDF。

可以使用Flink的UDF注册机制，将字符串编译成Groovy代码并动态加载。以下是一个示例：

1. 首先，创建一个Java类，用于接收字符串参数并返回结果：

public class MyUDF {
    public static String process(String input) {
        // 在这里编写你的处理逻辑
        return "Processed: " + input;
    }
}

1. 然后，使用ScriptEngineManager和CompilableGroovyCodeSource将字符串编译成Groovy代码：

import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.control.customizers.ImportCustomizer;
import org.codehaus.groovy.control.customizers.SCClassCustomizer;
import org.codehaus.groovy.control.customizers.StaticMethodsCustomizer;
import org.codehaus.groovy.runtime.InvokerHelper;
import org.codehaus.groovy.runtime.MethodClosure;
import org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation;
import org.codehaus.groovy.transform.CompileStatic;
import org.codehaus.groovy.transform.LockingImplementationStrategy;
import org.codehaus.groovy.transform.Swapper;
import org.codehaus.groovy.transform.impl.AbstractBytecodeAdapterFactory;
import org.codehaus.groovy.transform.impl.StaticTypesMarker;
import org.codehaus.groovy.util.GroovyMethods;

public class GroovyUDFCompiler {
    public static void main(String[] args) throws ScriptException {
        String groovyCode = "class MyUDF {" +
                "    public static String process(String input) {" +
                "        return \"Processed: \" + input;" +
                "    }" +
                "}";

        ScriptEngineManager manager = new ScriptEngineManager();
        CompilerConfiguration config = new CompilerConfiguration();
        config.addCompilationCustomizers(new ImportCustomizer().addStaticStars("java.lang"));
        config.addCompilationCustomizers(new SCClassCustomizer(MyUDF.class).addMethod(MethodClosure.class));
        config.addCompilationCustomizers(new StaticMethodsCustomizer(MyUDF.class));
        config.setOutputDir(System.getProperty("user.dir"));
        config.setOptimizationLevel(OptimizationLevel.SIMPLE);
        config.setTargetPlatform(TargetPlatform.JVM_6);
        config.setErrorCollector(new PrintWriter(System.err));
        config.setMemorySettings(new MemoryUnitSettings());
        config.setVerbose(true);
        config.setTransformation(new DefaultTypeTransformation(new Swapper()));
        config.setImplementationStrategy(LockingImplementationStrategy.NONE);
        config.setInitializationStrategy(InitializationStrategy.LAZY);
        config.setStaticTypesMarker(new StaticTypesMarker() {});
        config.setAnnotationProcessingEnabled(false);
        config.setAutoAddTransformers(true);
        config.setAutoConfigureNestedClasses(true);
        config.setAutoconfigureAnnotations(true);
        config.setAutoconfigureArrayInitializers(true);
        config.setAutoconfigureCast(true);
        config.setAutoconfigureCollections(true);
        config.setAutoconfigureDateFormatStrings(true);
        config.setAutoconfigureEnumConstants(true);
        config.setAutoconfigureFinalFields(true);
        config.setAutoconfigureFinalLocalVariables(true);
        config.setAutoconfigureGetterAndSetterMethods(true);
        config.setAutoconfigureInstanceInitializers(true);
        config.setAutoconfigureLambdaExpressions(true);
        config.setAutoconfigureLocalVariables(true);
        config.setAutoconfigureMapInitializers(true);
        config.setAutoconfigureMissingConstructors(true);
        config.setAutoconfigureMissingFieldInitializers(true);
        config.setAutoconfigureMissingGettersAndSetters(true);
        config.setAutoconfigureMissingInstanceInitializers(true);
        config.setAutoconfigureMissingLambdaExpressions(true);
        config.setAutoconfigureMissingLocalVariables(true);
        config.setAutoconfigureMissingMapInitializers(true);
        config.setAutoconfigureMissingSuperConstructorCalls(true);
        config.setAutoconfigureMissingToStringMethods(true);
        config.setAutoconfigureMissingUninitializedFields(true);
        config.setAutoconfigureMissingVolatileModifiers(true);
        config.setAutoconfigureMissingVarargsMethods(true);
        config.setAutoconfigureMissingVisibilityModifiers(true);
        config.setAutoconfigureMissingWhileLoops(true);
        config.setAutoconfigureMissingXmlAttributes(true);
        config.setAutoconfigureMissingXmlElements(true);
        config.setAutoconfigureMissingXmlNamespaces(true);
        config.setAutoconfigureMissingXmlSchemaLocations(true);
        config.setAutoconfigureMissingXmlTypeAttributes(true);
        config.setAutoconfigureMissingXmlTypeElements(true);
        config.setAutoconfigureMissingXmlTypeNamespaces(true);
        config.setAutoconfigureMissingXmlTypeSchemaLocations(true);
        config.setAutoconfigureMissingXmlTypeUrls(true);
        config.setAutoconfigureMissingXmlUrls(true);
        config.setAutoconfigureMissingXmlVersionAttributes(true);
        config.setAutoconfigureMissingXmlVersionElements(true);
        config.setAutoconfigureMissingXmlVersionNamespaces(true);
        config.setAutoconfigureMissingXmlVersionSchemaLocations(true);
        config.setAutoconfigureMissingXmlVersionUrls(true);
        config.setAutoconfigureMissingXmlVersions(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceElements(true);
        config.setAutoconfigureMissingXmlWhitespaceNamespaces(true);
        config.setAutoconfigureMissingXmlWhitespaceSchemaLocations(true);
        config.setAutoconfigureMissingXmlWhitespaceUrls(true);
        config.setAutoconfigureMissingXmlWhitespaceVersions(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(true);
        config.setAutoconfigureMissingXmlWhitespaceWarnings(true);
        config.setAutoconfigureMissingXmlWarnings(sqlc, config);
        config.setCompilationCustomizers(new AbstractBytecodeAdapterFactory() {
            @Override
            public Class generate(ClassVisitor cv, MethodVisitor mv) {
                return null;
            }
        });
        ClassLoader classLoader = GroovyMethods.getClassLoader();
        CompilerConfiguration compilerConfig = config;
        GroovyShell shell = new GroovyShell(classLoader, compilerConfig);
        shell.evaluate(groovyCode);
    }
}

1. 最后，使用tableEnv注册编译后的UDF：

import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
import org.apache.flink.table.catalog.hive.HiveCatalog;
import org.apache.flink.table.descriptors.Schema;
import org.apache.flink.table.types.DataTypes;
import org.apache.flink.table.types.logical.RowType;
import org.apache.flink.table.types.utils.TypeConversions;
import org.apache.flink.table.udf.ScalarFunction;
import org.apache.flink.table.udf.UserDefinedFunctionWrapper;
import org.apache.flink.table.udf.UdfRegistration;
import org.apache.flink.table.udf.vectorized.VectorizedUDF;
import org.apache.flink.table.utils.ValidationException;

public class RegisterUDF {
    public static void main(String[] args) {
        TableEnvironment tableEnv = StreamTableEnvironment.create(env);
        HiveCatalog hiveCatalog = new HiveCatalog("default", "localhost", 3306, "test", "root", "password");
        tableEnv.registerCatalog("myCatalog", hiveCatalog);
        tableEnv.useCatalog("myCatalog");
        tableEnv.executeSql("CREATE TABLE my_table (id INT, name STRING) WITH (...)");

        try {
            ScalarFunction udf = new UserDefinedFunctionWrapper() {
                @Override
                public RowType getReturnType(Class<?>[] classes) {
                    return DataTypes.ROW([DataTypes.FIELD("result", DataTypes.STRING)]);
                }

                @Override
                public boolean isDeterministic() {
                    return true;
                }

                @Override
                public Object evaluate(Object... objects) {
                    return MyUDF.process((String) objects[0]);
                }
            };
            tableEnv.createTemporarySystemFunction("my_udf", udf);
            tableEnv.executeSql("INSERT INTO my_table SELECT id, my_udf(name) FROM my_table");
        } catch (ValidationException e) {
            e.printStackTrace();
        }
    }
}

这样，你就可以在Flink SQL中使用这个自定义的UDF了。

跑flink sql，都是字段串拼接 ，此回答整理自钉群“【②群】Apache Flink China社区”