Fix class loading problem with DevTools and Spring Session with Redis

Previously, when a session attribute that had been stored in Redis was
being deserialized, the app class loader would be used. This would
result in a ClassCastException if the attribute was an instance of a
class visible to the restart class loader.

This commit auto-configures Spring Session’s RedisTemplate to use a
custom deserializer that uses the restart class loader when
deserializing session attributes.

Closes gh-3805

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfiguration.java

@@ -22,6 +22,7 @@ import java.util.List;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
@@ -40,12 +41,15 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.event.EventListener;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.session.ExpiringSession;
 import org.springframework.util.StringUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for local development support.
  *
  * @author Phillip Webb
+ * @author Andy Wilkinson
  * @since 1.3.0
  */
 @Configuration
@@ -159,6 +163,19 @@ public class LocalDevToolsAutoConfiguration {
 			return watcher;
 		}
 
+		@Configuration
+		@ConditionalOnBean(name = "sessionRedisTemplate")
+		static class RedisRestartConfiguration {
+
+			@Bean
+			public RestartCompatibleRedisSerializerConfigurer restartCompatibleRedisSerializerConfigurer(
+					RedisTemplate<String, ExpiringSession> sessionRedisTemplate) {
+				return new RestartCompatibleRedisSerializerConfigurer(
+						sessionRedisTemplate);
+			}
+
+		}
+
 	}
 
 }

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/RestartCompatibleRedisSerializerConfigurer.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2012-2015 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
+ *
+ *      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.springframework.boot.devtools.autoconfigure;
+
+import javax.annotation.PostConstruct;
+
+import org.springframework.beans.factory.BeanClassLoaderAware;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.serializer.DefaultDeserializer;
+import org.springframework.core.serializer.support.DeserializingConverter;
+import org.springframework.core.serializer.support.SerializingConverter;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.serializer.RedisSerializer;
+import org.springframework.data.redis.serializer.SerializationException;
+import org.springframework.session.ExpiringSession;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * Configures a {@link RedisTemplate} with a serializer for keys, values, hash keys, and
+ * hash values that is compatible with the split classloader used for restarts.
+ *
+ * @author Andy Wilkinson
+ * @author Rob Winch
+ *
+ * @see RedisTemplate#setHashKeySerializer(RedisSerializer)
+ * @see RedisTemplate#setHashValueSerializer(RedisSerializer)
+ * @see RedisTemplate#setKeySerializer(RedisSerializer)
+ * @see RedisTemplate#setValueSerializer(RedisSerializer)
+ */
+class RestartCompatibleRedisSerializerConfigurer implements BeanClassLoaderAware {
+
+	private final RedisTemplate<String, ExpiringSession> redisTemplate;
+
+	private volatile ClassLoader classLoader;
+
+	RestartCompatibleRedisSerializerConfigurer(
+			RedisTemplate<String, ExpiringSession> redisTemplate) {
+		this.redisTemplate = redisTemplate;
+	}
+
+	@Override
+	public void setBeanClassLoader(ClassLoader classLoader) {
+		this.classLoader = classLoader;
+	}
+
+	@PostConstruct
+	void configureTemplateSerializers() {
+		RestartCompatibleRedisSerializer serializer = new RestartCompatibleRedisSerializer(
+				this.classLoader);
+		this.redisTemplate.setHashKeySerializer(serializer);
+		this.redisTemplate.setHashValueSerializer(serializer);
+		this.redisTemplate.setKeySerializer(serializer);
+		this.redisTemplate.setValueSerializer(serializer);
+	}
+
+	static class RestartCompatibleRedisSerializer implements RedisSerializer<Object> {
+
+		private final Converter<Object, byte[]> serializer = new SerializingConverter();
+
+		private final Converter<byte[], Object> deserializer;
+
+		RestartCompatibleRedisSerializer(ClassLoader classLoader) {
+			this.deserializer = new DeserializingConverter(
+					new DefaultDeserializer(classLoader));
+		}
+
+		@Override
+		public Object deserialize(byte[] bytes) {
+			if (ObjectUtils.isEmpty(bytes)) {
+				return null;
+			}
+
+			try {
+				return this.deserializer.convert(bytes);
+			}
+			catch (Exception ex) {
+				throw new SerializationException("Cannot deserialize", ex);
+			}
+		}
+
+		@Override
+		public byte[] serialize(Object object) {
+			if (object == null) {
+				return new byte[0];
+			}
+			try {
+				return this.serializer.convert(object);
+			}
+			catch (Exception ex) {
+				throw new SerializationException("Cannot serialize", ex);
+			}
+		}
+
+	}
+
+}

spring-boot-devtools/src/test/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfigurationTests.java

@@ -31,6 +31,7 @@ import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.ResourceProperties;
+import org.springframework.boot.devtools.autoconfigure.RestartCompatibleRedisSerializerConfigurer.RestartCompatibleRedisSerializer;
 import org.springframework.boot.devtools.classpath.ClassPathChangedEvent;
 import org.springframework.boot.devtools.classpath.ClassPathFileSystemWatcher;
 import org.springframework.boot.devtools.filewatch.ChangedFiles;
@@ -44,6 +45,9 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.data.redis.connection.RedisConnectionFactory;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.session.ExpiringSession;
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.util.SocketUtils;
 
@@ -63,6 +67,7 @@ import static org.mockito.Mockito.verify;
  * Tests for {@link LocalDevToolsAutoConfiguration}.
  *
  * @author Phillip Webb
+ * @author Andy Wilkinson
  */
 public class LocalDevToolsAutoConfigurationTests {
 
@@ -235,6 +240,24 @@ public class LocalDevToolsAutoConfigurationTests {
 		assertThat(folders, hasKey(new File("src/test/java").getAbsoluteFile()));
 	}
 
+	@Test
+	public void sessionRedisTemplateIsConfiguredWithCustomDeserializers()
+			throws Exception {
+		SpringApplication application = new SpringApplication(
+				SessionRedisTemplateConfig.class, LocalDevToolsAutoConfiguration.class);
+		application.setWebEnvironment(false);
+		this.context = application.run();
+		RedisTemplate<?, ?> redisTemplate = this.context.getBean(RedisTemplate.class);
+		assertThat(redisTemplate.getHashKeySerializer(),
+				is(instanceOf(RestartCompatibleRedisSerializer.class)));
+		assertThat(redisTemplate.getHashValueSerializer(),
+				is(instanceOf(RestartCompatibleRedisSerializer.class)));
+		assertThat(redisTemplate.getKeySerializer(),
+				is(instanceOf(RestartCompatibleRedisSerializer.class)));
+		assertThat(redisTemplate.getValueSerializer(),
+				is(instanceOf(RestartCompatibleRedisSerializer.class)));
+	}
+
 	private ConfigurableApplicationContext initializeAndRun(Class<?> config,
 			String... args) {
 		return initializeAndRun(config, Collections.<String, Object>emptyMap(), args);
@@ -282,4 +305,16 @@ public class LocalDevToolsAutoConfigurationTests {
 
 	}
 
+	@Configuration
+	public static class SessionRedisTemplateConfig {
+
+		@Bean
+		public RedisTemplate<String, ExpiringSession> sessionRedisTemplate() {
+			RedisTemplate<String, ExpiringSession> redisTemplate = new RedisTemplate<String, ExpiringSession>();
+			redisTemplate.setConnectionFactory(mock(RedisConnectionFactory.class));
+			return redisTemplate;
+		}
+
+	}
+
 }