无法从String值(‘{‘)实例化java.util.LinkedHashMap类型的值;

@JsonIgnoreProperties(ignoreUnknown = true)
public class ChangesJSON {

    @JsonProperty("changes")
    List<ChangeJSON> changes;

    @JsonProperty("more")
    Boolean more;
}

public class ChangeJSON {

    @JsonProperty("epoch")
    Long epoch;

    @JsonProperty("payload")
    Map<String,Object> payload;
}

当我尝试使用此测试反序列化时：

String test = "{"changes":[{"epoch":1441556306522,"payload":"{"to":1}"},{"epoch":1441555481524,"payload":"{"to":-1}"}],"more":false}";

@Test
public void myTest() {
    ObjectMapper mapper = new ObjectMapper();
    ChangesJSON result = null;
    try {
        result = mapper.readValue(test,ChangesJSON.class);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    assertNotNull(result);
}

我得到以下异常：

com.fasterxml.jackson.databind.JsonMappingException: Can not
instantiate value of type java.util.LinkedHashMap from String value
(‘{‘); no single-String constructor/factory method at [Source:
{“changes”:[{“epoch”:1441556306522,”payload”:”{“to”:1}”},{“epoch”:1441555481524,”payload”:”{“to”:-1}”}],”more”:false};
line: 1,column: 35] (through reference chain:
demo.ChangesJSON[“changes”]->java.util.ArrayList[0]->demo.ChangeJSON[“payload”])

似乎地图存在问题,但我认为杰克逊应该能够处理地图.当我将地图更改为Map时,我也遇到了同样的问题.但我确实需要支持各种类作为地图的值.