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我有以下我试图反序列化的 JSON 文件：

{
    "name": "ComponentX",
    "implements": ["Temperature.Sensor"],
    "requires": [
        {"type": "interface", "name": "Temperature.Thermostat", "execute": [
            "../Thermostat.exe"
        ]}
    ]
}

它是分布式系统代码示例中组件的描述。

这是应该反序列化的类：

public class ComponentDescription {
    @JsonProperty("name")
    public String Name;

    @JsonProperty("implements")
    public String[] Implements;

    @JsonProperty("requires")
    public ComponentDependency[] Requires;

    @JsonIgnore
    public String RabbitConnectionName;

    private static final ObjectMapper mapper = new ObjectMapper();

    public static ComponentDescription FromJSON(String json)
        throws JsonParseException, JsonMappingException, IOException
    {
        return mapper.readValue(json, ComponentDescription.class);
    }

    public class ComponentDependency
    {
        @JsonCreator
        public ComponentDependency() {
            // Need an explicit default constructor in order to use Jackson.
        }

        @JsonProperty("type")
        public DependencyType Type;

        @JsonProperty("name")
        public String Name;

        /**
         * A list of ways to start the required component if it is not already running.
         */
        @JsonProperty("execute")
        public String[] Execute;
    }

    /**
     * A dependency can either be on "some implementation of an interface" or it
     * can be "a specific component", regardless of what other interface implementations
     * may be available.
     */
    public enum DependencyType
    {
        Interface,
        Component
    }
}

当我运行时ComponentDescription.FromJSON(jsonData)，它使用 Jackson ObjectMapper 将 JSON 反序列化为适当的类，我得到以下异常：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "type" (class edu.umd.cs.seam.dispatch.ComponentDescription), not marked as ignorable (3 known properties: , "implements", "name", "requires"])
 at [Source: java.io.StringReader@39346e64; line: 1, column: 103] (through reference chain: edu.umd.cs.seam.dispatch.ComponentDescription["requires"]->edu.umd.cs.seam.dispatch.ComponentDescription["type"])

似乎杰克逊试图将requiresJSON 对象中的数组反序列化为数组ComponentDescription而不是ComponentDependency. 如何让它使用正确的类？我更喜欢让杰克逊查看类型public ComponentDependency[] Requires并自动使用它的答案，而不是要求我再次将类型名称放入其他地方（例如@属性）的答案。

4

1 回答 1

3

我的猜测是问题来自于ComponentDependencynot being static。由于它没有被声明static，这意味着它只能用 的现有实例来实例化ComponentDescription。

有关更多详细信息，请参见此处。

于 2013-06-23T18:29:47.857 回答