@ResponseBody遇到问题

1.No converter found for return value of type: class java.util.ArrayList

• springmvc 默认是没有对象转换成json的转换器的 手动添加jackson依赖

<!--    jackson-->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.11.0</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.11.0</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.11.0</version>
    </dependency>