使用jackson反序列化为自定义对象的HashMap

I have the following class:

我有以下课程：

import org.codehaus.jackson.annotate.JsonIgnoreProperties;
import org.codehaus.jackson.annotate.JsonProperty;

import java.io.Serializable;
import java.util.HashMap;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Theme implements Serializable {

    @JsonProperty
    private String themeName;

    @JsonProperty
    private boolean customized;

    @JsonProperty
    private HashMap<String, String> descriptor;

    //...getters and setters for the above properties
}

When I execute the following code:

当我执行以下代码时：

    HashMap<String, Theme> test = new HashMap<String, Theme>();
    Theme t1 = new Theme();
    t1.setCustomized(false);
    t1.setThemeName("theme1");
    test.put("theme1", t1);

    Theme t2 = new Theme();
    t2.setCustomized(true);
    t2.setThemeName("theme2");
    t2.setDescriptor(new HashMap<String, String>());
    t2.getDescriptor().put("foo", "one");
    t2.getDescriptor().put("bar", "two");
    test.put("theme2", t2);
    String json = "";
    ObjectMapper mapper = objectMapperFactory.createObjectMapper();
    try {
        json = mapper.writeValueAsString(test);
    } catch (IOException e) {
        e.printStackTrace(); 
    }

The json string produced looks like this:

生成的json字符串如下所示：

{
  "theme2": {
    "themeName": "theme2",
    "customized": true,
    "descriptor": {
      "foo": "one",
       "bar": "two"
    }
  },
  "theme1": {
    "themeName": "theme1",
    "customized": false,
    "descriptor": null
  }
}

My problem is getting the above json string to de-serizlize back into a

我的问题是让上面的json字符串去反序列化

HashMap<String, Theme>

object.

目的。

My de-serialization code looks like this:

我的反序列化代码如下所示：

HashMap<String, Themes> themes =
        objectMapperFactory.createObjectMapper().readValue(json, HashMap.class);

Which de-serializes into a HashMap with the correct keys, but does not create Theme objects for the values. I don't know what to specify instead of "HashMap.class" in the readValue() method.

使用正确的密钥将其反序列化为HashMap，但不为值创建Theme对象。我不知道在readValue（）方法中指定什么而不是“HashMap.class”。

Any help would be appreciated.

任何帮助，将不胜感激。

3 个解决方案

#1

You should create specific Map type and provide it into deserialization process:

您应该创建特定的Map类型并将其提供给反序列化过程：

TypeFactory typeFactory = mapper.getTypeFactory();
MapType mapType = typeFactory.constructMapType(HashMap.class, String.class, Theme.class);
HashMap<String, Theme> map = mapper.readValue(json, mapType);

#2

You can use TypeReference class which does the type casting for map with user defined types. More documentation at http://wiki.fasterxml.com/JacksonInFiveMinutes

您可以使用TypeReference类，它为具有用户定义类型的map执行类型转换。有关http://wiki.fasterxml.com/JacksonInFiveMinutes的更多文档

ObjectMapper mapper = new ObjectMapper();
Map<String,Theme> result =
  mapper.readValue(src, new TypeReference<Map<String,Theme>>() {});

#3

You can make a POJO that extends a Map.

您可以创建一个扩展Map的POJO。

This is important for dealing with nested maps of objects.

这对于处理嵌套的对象映射很重要。

{
  key1: { nestedKey1: { value: 'You did it!' } }
}

This can be deserialized via:

这可以通过以下方式反序列化：

class Parent extends HashMap<String, Child> {}

class Child extends HashMap<String, MyCoolPojo> {}

class MyCoolPojo { public String value; }

Parent parent = new ObjectMapper().readValue(json, Parent.class);
parent.get("key1").get("nestedKey1").value; // "You did it!"

#1