1.背景

Spring boot 启动报错

Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class java.util.LinkedHashMap

出现以上错误，原因在于，缺少了springmvc进行json转换需要的jar包，引入对应jar依赖：

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.9.6</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>2.9.6</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.9.6</version></dependency>

另外在pom文件中如果引入springboot-web依赖排除掉了springboot-web自带的json也会导致上面的异常信息：

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><exclusions><exclusion><artifactId>spring-boot-starter-json</artifactId><groupId>org.springframework.boot</groupId></exclusion></exclusions></dependency>

此时，需要将依赖改为以下即可：

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>

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