Spring Boot项目Rest API返回XML而非JSON问题求助

近期维护Spring Boot项目时遇到异常：原本返回JSON格式的Rest API，现在返回XML格式了。曾将Spring Boot版本从2.7.4升级至2.7.7，但回退到2.7.4后问题仍未解决。项目的Pom.xml配置如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.4</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.aryan.blogging</groupId>
    <artifactId>blogging-apis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>blogging-apis</name>
    <description>Backend for Blogging Application</description>
    <properties>
        <java.version>17</java.version>
        <spring-cloud-azure.version>4.5.0</spring-cloud-azure.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
         <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency> 
        
        <dependency>
            <groupId>com.microsoft.sqlserver</groupId>
            <artifactId>mssql-jdbc</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        
        <!-- ModelMapper -->
        <!-- https://mvnrepository.com/artifact/org.modelmapper/modelmapper -->
        <dependency>
            <groupId>org.modelmapper</groupId>
            <artifactId>modelmapper</artifactId>
            <version>3.1.0</version>
        </dependency>
        <!-- Hibernate Spring Validator -->
        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-validation -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>

        <!-- Spring Security -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <!-- JWT -->
        <!-- https://mvnrepository.com/artifact/io.jsonwebtoken/jjwt -->
        <dependency>
            <groupId>io.jsonwebtoken</groupId>
            <artifactId>jjwt</artifactId>
            <version>0.9.1</version>
        </dependency>

        <!-- Swagger -->
        <!-- https://mvnrepository.com/artifact/io.springfox/springfox-boot-starter -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-boot-starter</artifactId>
            <version>3.0.0</version>
        </dependency>
  <!-- https://mvnrepository.com/artifact/com.sun.mail/jakarta.mail -->
<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
    <dependency>
            <groupId>com.azure.spring</groupId>
            <artifactId>spring-cloud-azure-starter-storage</artifactId>
        </dependency>
<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
<!-- Added from
        https://learn.microsoft.com/en-us/azure/developer/java/spring-framework/configure-spring-boot-starter-java-app-with-azure-storage-->
        <dependency>
            <groupId>com.azure.spring</groupId>
            <artifactId>spring-cloud-azure-starter-storage-blob</artifactId>
        </dependency>
        
        <!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>31.1-jre</version>
</dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.azure.spring</groupId>
                <artifactId>spring-cloud-azure-dependencies</artifactId>
                <version>${spring-cloud-azure.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

排查与解决步骤 #

1. 检查Jackson XML依赖是否被间接引入 #

Spring Boot默认用Jackson处理JSON，但如果类路径中存在jackson-dataformat-xml依赖，Spring MVC会优先选择XML作为响应格式。你的pom.xml虽未直接引入，但Azure组件、Swagger等依赖可能间接带入该包。

• 执行Maven命令查看依赖树：

mvn dependency:tree | grep jackson-dataformat-xml

• 若发现该依赖，在对应的父依赖中排除它，例如：

<dependency>
    <groupId>com.azure.spring</groupId>
    <artifactId>spring-cloud-azure-starter-storage-blob</artifactId>
    <exclusions>
        <exclusion>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-xml</artifactId>
        </exclusion>
    </exclusions>
</dependency>

2. 全局强制指定JSON为默认响应格式 #

在application.properties或application.yml中添加配置：

spring.mvc.contentnegotiation.favor-parameter=false
spring.mvc.contentnegotiation.default-content-type=application/json

3. 局部注解指定响应格式 #

在Controller方法上明确指定返回JSON：

@GetMapping(value = "/api/xxx", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<?> yourApiMethod() {
    // 业务逻辑
}

4. 检查请求头Accept参数 #

客户端请求时若携带Accept: application/xml，Spring MVC会返回XML。通过开发者工具或接口测试工具查看请求头，若为前端误传则修正请求；若需忽略该参数，可通过上述全局配置关闭内容协商的参数支持。

5. 调整MessageConverter优先级 #

自定义Web配置，确保JSON转换器优先级高于XML转换器：

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.removeIf(converter -> converter instanceof MappingJackson2XmlHttpMessageConverter);
        converters.add(new MappingJackson2HttpMessageConverter());
    }
}

内容的提问来源于stack exchange，提问作者Aryan Singh