使用Jackson ObjectMapper将Json的一部分转换为HashMap

Question

我试图以一种方式解组json文件,使得Json的少数属性被映射到我的模型类中存在的HashMap.属性的重置被映射到类的相应字段.请在下面找到Json:

{
         "_id":2,
         "Name":"xyz",
         "Age":20,
         "MEMO_TEXT":"yyy",
         "MEMO_LINK":"zzz",
         "MEMO_DOB":"",
         "MEMO_USERNAME":"linie orange",
         "MEMO_CATEGORY":2,
         "MEMO_UID":"B82071415B07495F9DD02C152E4805EC"
      }

这里是我要映射这个Json的Model类:

public class Model{

    private int                              _id;
    private String                           name;
    private int                              age
    private HashMap<String, String> columns;

    //Getters and Setter methods
}

所以在这里,我想要的是获得一个columns包含密钥的地图"MEMO_TEXT","MEMO_LINK","MEMO_DOB","MEMO_USERNAME","MEMO_CATEGORY","MEMO_UID"

Json中的其余属性映射到它们各自的字段.

是否可以使用杰克逊图书馆的ObjectMapper来做到这一点？

Answer 1

您可以使用@JsonAnySetter来注释要为"其他"属性调用的方法:

@Test
public void partial_binding() throws Exception {
    Model model = mapper.readValue(Resources.getResource("partial_binding.json"), Model.class);
    assertThat(model.name, equalTo("xyz"));
    assertThat(model.columns, hasEntry("MEMO_TEXT", "yyy"));
    assertThat(
            mapper.writeValueAsString(model),
            json(jsonObject()
                 .withProperty("Name", "xyz")
                 .withProperty("MEMO_TEXT", "yyy")
                 .withAnyOtherProperties()));
}

public static class Model {
    @JsonProperty
    private int _id;
    @JsonProperty("Name")
    private String name;
    @JsonProperty("Age")
    private int age;
    private HashMap<String, String> columns;

    @JsonAnyGetter
    public HashMap<String, String> getColumns() {
        return columns;
    }

    public void setColumns(HashMap<String, String> columns) {
        this.columns = columns;
    }

    @JsonAnySetter
    public void putColumn(String key, String value) {
        if (columns == null) columns = new HashMap<>();
        columns.put(key, value);
    }
}

此外,@ JsonAnyGetter做了"反向",所以这应该以相同的方式序列化和反序列化.