Add common Expression to String Converter (#50)

* Add common Expression to String Converter

Co-authored-by: David Turanski <dturanski@pivotal.io>

common/config-common/pom.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>config-common</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <name>geode-common</name>
+    <description>Function Common Configuration Components</description>
+
+    <parent>
+        <groupId>org.springframework.cloud.fn</groupId>
+        <artifactId>spring-functions-parent</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../spring-functions-parent</relativePath>
+    </parent>
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.integration</groupId>
+            <artifactId>spring-integration-core</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

common/config-common/src/main/java/org/springframework/cloud/fn/common/config/SpelExpressionConverterConfiguration.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2020-2020 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.cloud.fn.common.config;
+
+import java.beans.Introspector;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.boot.context.properties.ConfigurationPropertiesBinding;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Lazy;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.Expression;
+import org.springframework.expression.ParseException;
+import org.springframework.expression.spel.standard.SpelExpression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.integration.config.IntegrationConverter;
+import org.springframework.integration.expression.SpelPropertyAccessorRegistrar;
+import org.springframework.integration.json.JsonPropertyAccessor;
+
+@Configuration
+public class SpelExpressionConverterConfiguration {
+	@Bean
+	public static SpelPropertyAccessorRegistrar spelPropertyAccessorRegistrar() {
+		return (new SpelPropertyAccessorRegistrar())
+				.add(Introspector.decapitalize(JsonPropertyAccessor.class.getSimpleName()), new JsonPropertyAccessor());
+	}
+
+	@Bean
+	@ConfigurationPropertiesBinding
+	@IntegrationConverter
+	public Converter<String, Expression> spelConverter() {
+		return new SpelExpressionConverterConfiguration.SpelConverter();
+	}
+
+	public static class SpelConverter implements Converter<String, Expression> {
+		private SpelExpressionParser parser = new SpelExpressionParser();
+
+		@Autowired
+		@Qualifier("integrationEvaluationContext")
+		@Lazy
+		private EvaluationContext evaluationContext;
+
+		public SpelConverter() {
+		}
+
+		public Expression convert(String source) {
+			try {
+				Expression expression = this.parser.parseExpression(source);
+				if (expression instanceof SpelExpression) {
+					((SpelExpression) expression).setEvaluationContext(this.evaluationContext);
+				}
+
+				return expression;
+			}
+			catch (ParseException var3) {
+				throw new IllegalArgumentException(
+						String.format("Could not convert '%s' into a SpEL expression", source), var3);
+			}
+		}
+	}
+}

common/config-common/src/main/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
+  org.springframework.cloud.fn.common.config.SpelExpressionConverterConfiguration

pom.xml

@@ -41,6 +41,7 @@
 	</properties>
 
   	<modules>
+		<module>common/config-common</module>
 		<module>common/ftp-common</module>
 		<module>common/function-test-support</module>
 		<module>common/tcp-common</module>