No converter found for return value of type: class XXX

今天使用springboot开发一个小demo,后端采用json返回数据,但是前端访问时出现错误.
前端错误如下:

后端错误如下:

"D:\Program Files\Java\jdk1.8.0_152\bin\java.exe" -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:51563,suspend=y,server=n -XX:TieredStopAtLevel=1 -noverify -Dspring.output.ansi.enabled=always -Dcom.sun.management.jmxremote -Dspring.jmx.enabled=true -Dspring.liveBeansView.mbeanDomain -Dspring.application.admin.enabled=true -javaagent:C:\Users\Administrator\.IntelliJIdea2019.2\system\captureAgent\debugger-agent.jar -Dfile.encoding=UTF-8 -classpath "D:\Program Files\Java\jdk1.8.0_152\jre\lib\charsets.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\deploy.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\access-bridge-64.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\cldrdata.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\dnsns.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jaccess.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jfxrt.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\localedata.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\nashorn.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunec.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunjce_provider.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunmscapi.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunpkcs11.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\zipfs.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\javaws.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\jce.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\jfr.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\jfxswt.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\jsse.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\management-agent.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\plugin.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\resources.jar;D:\Program Files\Java\jdk1.8.0_152\jre\lib\rt.jar;D:\Workspace4Exercise\exercise\friday\target\classes;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-thymeleaf\2.3.3.RELEASE\spring-boot-starter-thymeleaf-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter\2.3.3.RELEASE\spring-boot-starter-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot\2.3.3.RELEASE\spring-boot-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-autoconfigure\2.3.3.RELEASE\spring-boot-autoconfigure-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-logging\2.3.3.RELEASE\spring-boot-starter-logging-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;D:\apache-maven-3.5.2\repo\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;D:\apache-maven-3.5.2\repo\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;D:\apache-maven-3.5.2\repo\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;D:\apache-maven-3.5.2\repo\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;D:\apache-maven-3.5.2\repo\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\apache-maven-3.5.2\repo\org\yaml\snakeyaml\1.26\snakeyaml-1.26.jar;D:\apache-maven-3.5.2\repo\org\thymeleaf\thymeleaf-spring5\3.0.11.RELEASE\thymeleaf-spring5-3.0.11.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\thymeleaf\thymeleaf\3.0.11.RELEASE\thymeleaf-3.0.11.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\attoparser\attoparser\2.0.5.RELEASE\attoparser-2.0.5.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\unbescape\unbescape\1.1.6.RELEASE\unbescape-1.1.6.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;D:\apache-maven-3.5.2\repo\org\thymeleaf\extras\thymeleaf-extras-java8time\3.0.4.RELEASE\thymeleaf-extras-java8time-3.0.4.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-web\2.3.3.RELEASE\spring-boot-starter-web-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-json\2.3.3.RELEASE\spring-boot-starter-json-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\core\jackson-databind\2.11.2\jackson-databind-2.11.2.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\core\jackson-annotations\2.11.2\jackson-annotations-2.11.2.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\core\jackson-core\2.11.2\jackson-core-2.11.2.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.11.2\jackson-datatype-jdk8-2.11.2.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.11.2\jackson-datatype-jsr310-2.11.2.jar;D:\apache-maven-3.5.2\repo\com\fasterxml\jackson\module\jackson-module-parameter-names\2.11.2\jackson-module-parameter-names-2.11.2.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-tomcat\2.3.3.RELEASE\spring-boot-starter-tomcat-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\apache\tomcat\embed\tomcat-embed-core\9.0.37\tomcat-embed-core-9.0.37.jar;D:\apache-maven-3.5.2\repo\org\glassfish\jakarta.el\3.0.3\jakarta.el-3.0.3.jar;D:\apache-maven-3.5.2\repo\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.37\tomcat-embed-websocket-9.0.37.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-web\5.2.8.RELEASE\spring-web-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-beans\5.2.8.RELEASE\spring-beans-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-webmvc\5.2.8.RELEASE\spring-webmvc-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-aop\5.2.8.RELEASE\spring-aop-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-context\5.2.8.RELEASE\spring-context-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-expression\5.2.8.RELEASE\spring-expression-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\mybatis\spring\boot\mybatis-spring-boot-starter\2.1.3\mybatis-spring-boot-starter-2.1.3.jar;D:\apache-maven-3.5.2\repo\org\springframework\boot\spring-boot-starter-jdbc\2.3.3.RELEASE\spring-boot-starter-jdbc-2.3.3.RELEASE.jar;D:\apache-maven-3.5.2\repo\com\zaxxer\HikariCP\3.4.5\HikariCP-3.4.5.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-jdbc\5.2.8.RELEASE\spring-jdbc-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-tx\5.2.8.RELEASE\spring-tx-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\mybatis\spring\boot\mybatis-spring-boot-autoconfigure\2.1.3\mybatis-spring-boot-autoconfigure-2.1.3.jar;D:\apache-maven-3.5.2\repo\org\mybatis\mybatis\3.5.5\mybatis-3.5.5.jar;D:\apache-maven-3.5.2\repo\org\mybatis\mybatis-spring\2.0.5\mybatis-spring-2.0.5.jar;D:\apache-maven-3.5.2\repo\mysql\mysql-connector-java\8.0.21\mysql-connector-java-8.0.21.jar;D:\apache-maven-3.5.2\repo\com\alibaba\druid\1.1.10\druid-1.1.10.jar;D:\apache-maven-3.5.2\repo\org\projectlombok\lombok\1.18.12\lombok-1.18.12.jar;D:\apache-maven-3.5.2\repo\com\google\guava\guava\27.0-jre\guava-27.0-jre.jar;D:\apache-maven-3.5.2\repo\com\google\guava\failureaccess\1.0\failureaccess-1.0.jar;D:\apache-maven-3.5.2\repo\com\google\guava\listenablefuture\9999.0-empty-to-avoid-conflict-with-guava\listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar;D:\apache-maven-3.5.2\repo\com\google\code\findbugs\jsr305\3.0.2\jsr305-3.0.2.jar;D:\apache-maven-3.5.2\repo\org\checkerframework\checker-qual\2.5.2\checker-qual-2.5.2.jar;D:\apache-maven-3.5.2\repo\com\google\errorprone\error_prone_annotations\2.2.0\error_prone_annotations-2.2.0.jar;D:\apache-maven-3.5.2\repo\com\google\j2objc\j2objc-annotations\1.1\j2objc-annotations-1.1.jar;D:\apache-maven-3.5.2\repo\org\codehaus\mojo\animal-sniffer-annotations\1.17\animal-sniffer-annotations-1.17.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-core\5.2.8.RELEASE\spring-core-5.2.8.RELEASE.jar;D:\apache-maven-3.5.2\repo\org\springframework\spring-jcl\5.2.8.RELEASE\spring-jcl-5.2.8.RELEASE.jar;D:\OpenSources\JetBrains\IntelliJ IDEA 2019.2.4\lib\idea_rt.jar" com.xsh.friday.FridayApplication
Connected to the target VM, address: '127.0.0.1:51563', transport: 'socket'

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.3.RELEASE)

2020-09-01 22:26:50.169  INFO 9124 --- [           main] com.xsh.friday.FridayApplication         : Starting FridayApplication on SAMSUNG with PID 9124 (D:\Workspace4Exercise\exercise\friday\target\classes started by Administrator in D:\Workspace4Exercise\exercise\friday)
2020-09-01 22:26:50.178  INFO 9124 --- [           main] com.xsh.friday.FridayApplication         : The following profiles are active: dev
2020-09-01 22:26:53.390  INFO 9124 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-09-01 22:26:53.406  INFO 9124 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-09-01 22:26:53.406  INFO 9124 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-09-01 22:26:53.570  INFO 9124 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-09-01 22:26:53.571  INFO 9124 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 3092 ms
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
2020-09-01 22:26:55.087  INFO 9124 --- [           main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-1} inited
2020-09-01 22:26:55.881  INFO 9124 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-09-01 22:26:56.007  INFO 9124 --- [           main] o.s.b.a.w.s.WelcomePageHandlerMapping    : Adding welcome page template: index
2020-09-01 22:26:56.334  INFO 9124 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-09-01 22:26:56.362  INFO 9124 --- [           main] com.xsh.friday.FridayApplication         : Started FridayApplication in 8.148 seconds (JVM running for 10.689)
2020-09-01 22:27:03.221  INFO 9124 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-09-01 22:27:03.221  INFO 9124 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-09-01 22:27:03.241  INFO 9124 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 19 ms
2020-09-01 22:27:03.711  WARN 9124 --- [nio-8080-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class com.xsh.friday.base.result.Results]

是因为在Results类中没有getter/setter方法