Spring Boot 2.7 Upgrade Pitfalls and Solutions

The author shares a thorough summary of the pitfalls encountered when upgrading a Spring Boot project to version 2.7, aiming to help developers avoid common errors.

Prerequisites: 2.7.2 is the last stable 2.x release and requires Java 17; the following fixes are specific to the author's project and may need adaptation.

1. Hibernate‑Validator missing: Starting with Spring Boot 2.3, <dependency> <groupId>org.hibernate.validator</groupId> <artifactId>hibernate-validator</artifactId> <version>6.0.18.Final</version> <scope>compile</scope> </dependency> must be added manually in the parent POM.

2. ErrorController getErrorPath removed: Simply delete the getErrorPath() method from the custom ErrorController .

3. Logback vs Log4j conflict: Exclude Spring Boot's default Logback logging and add Log4j2 explicitly: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-batch</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-logging</artifactId> </exclusion> </exclusions> </dependency> .

4. Circular bean dependency: Remove the problematic method and handlerAdapter from WebMainConfig , and define a conversion service bean to avoid the cycle: @Bean public ConversionService getConversionService(DateConverter dateConverter) { ConversionServiceFactoryBean factoryBean = new ConversionServiceFactoryBean(); Set > converters = new HashSet<>(); converters.add(dateConverter); factoryBean.setConverters(converters); return factoryBean.getObject(); } . A global date converter can be implemented as: @Configuration public class DateConverter implements Converter { @Override public Date convert(String source) { return DateUtil.parse(source); } } . If a cycle is unavoidable, enable it with spring.main.allow-circular-references=true or annotate beans with @Lazy .

5. Swagger bean start failure: Spring Boot 2.6+ switches the path‑matching strategy to PathPatternParser , causing Swagger to fail. Restore the old matcher: spring.mvc.pathmatch.matching-strategy=ANT_PATH_MATCHER . Upgrade Swagger to version 3 or switch to Knife4j: add <dependency> <groupId>com.github.xiaoymin</groupId> <artifactId>knife4j-spring-boot-starter</artifactId> <version>3.0.3</version> </dependency> and rename the config class to SwaggerConfig (remove @EnableSwagger2 ).

6. Login page forward error: The same configuration change in step 5 resolves the “Cannot forward to error page” issue.

7. Date conversion to LocalDateTime: Adjust MyBeanProcessor to handle LocalDateTime and LocalDate types, e.g.: if (value.getClass().equals(LocalDateTime.class)) { field.set(model, DateTimeUtil.localDateTime2Date((LocalDateTime) value)); } else if (value.getClass().equals(LocalDate.class)) { field.set(model, DateTimeUtil.localDate2Date((LocalDate) value)); } .

8. Flyway unsupported MySQL 5.7: Flyway 8.x does not support MySQL 5.7. Downgrade Flyway to 7.15.0 (or another compatible version) in the pom.xml : <flyway.version>7.15.0</flyway.version> <dependency> <groupId>org.flywaydb</groupId> <artifactId>flyway-core</artifactId> <version>${flyway.version}</version> </dependency> .

9. JUnit5 vs JUnit4 conflict: After the upgrade, JUnit 5 is used by default. Remove JUnit 4 dependencies and replace annotations: org.junit.Test → org.junit.jupiter.api.Test , org.junit.runner.RunWith → org.junit.jupiter.api.extension.ExtendWith , e.g., @RunWith(SpringRunner.class) → @ExtendWith(SpringExtension.class) .

10. Long precision loss in JSON: The custom FastJsonHttpMessageConverter must be placed at the beginning of the converters list and configured to serialize Long and BigInteger as strings: converters.add(0, fastConverter); converters.add(0, new StringHttpMessageConverter(StandardCharsets.UTF_8)); converters.add(0, customJackson2HttpMessageConverter()); SerializeConfig serializeConfig = SerializeConfig.globalInstance; serializeConfig.put(BigInteger.class, ToStringSerializer.instance); serializeConfig.put(Long.class, ToStringSerializer.instance); serializeConfig.put(Long.TYPE, ToStringSerializer.instance); fastJsonConfig.setSerializeConfig(serializeConfig); .

The article concludes with a request for likes, follows, and shares, and provides links to PDF collections of related Spring Cloud, Spring Boot, and MyBatis tutorials.