java - 使用 Jackson 打印 json 数组

Question

我正在编写一个程序，需要从json文件中获取一些数据，内容如下。

{
    "culture": "en-us",
    "subscription_key": "myKey",
    "description": "myDescription",
    "name": "myName",
    "appID": "myAppId",
    "entities": [
        {
            "name": "Location"
        },
        {
            "name": "geography"
        }
    ]
}

使用在线工具，我已经为其创建了 POJO。它们如下。

ConfigDetails Pojo

package com.config;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
    "culture",
    "subscription_key",
    "description",
    "name",
    "appID",
    "entities"
})
public class ConfigDetails {

    @JsonProperty("culture")
    private String culture;
    @JsonProperty("subscription_key")
    private String subscriptionKey;
    @JsonProperty("description")
    private String description;
    @JsonProperty("name")
    private String name;
    @JsonProperty("appID")
    private String appID;
    @JsonProperty("entities")
    private List<Entity> entities = null;

    @JsonProperty("culture")
    public String getCulture() {
        return culture;
    }

    @JsonProperty("culture")
    public void setCulture(String culture) {
        this.culture = culture;
    }

    @JsonProperty("subscription_key")
    public String getSubscriptionKey() {
        return subscriptionKey;
    }

    @JsonProperty("subscription_key")
    public void setSubscriptionKey(String subscriptionKey) {
        this.subscriptionKey = subscriptionKey;
    }

    @JsonProperty("description")
    public String getDescription() {
        return description;
    }

    @JsonProperty("description")
    public void setDescription(String description) {
        this.description = description;
    }

    @JsonProperty("name")
    public String getName() {
        return name;
    }

    @JsonProperty("name")
    public void setName(String name) {
        this.name = name;
    }

    @JsonProperty("appID")
    public String getAppID() {
        return appID;
    }

    @JsonProperty("appID")
    public void setAppID(String appID) {
        this.appID = appID;
    }

    @JsonProperty("entities")
    public List<Entity> getEntities() {
        return entities;
    }

    @JsonProperty("entities")
    public void setEntities(List<Entity> entities) {
        this.entities = entities;
    }
}

实体 POJO

package com.config;

import java.util.HashMap;
import java.util.Map;
import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
    "name"
})
public class Entity {

    @JsonProperty("name")
    private String name;

    @JsonProperty("name")
    public String getName() {
        return name;
    }

    @JsonProperty("name")
    public void setName(String name) {
        this.name = name;
    }
}

我使用下面的代码来打印文件中的值。

MainClass obj = new MainClass();
        ObjectMapper mapper = new ObjectMapper();

        try {

            // Convert JSON string from file to Object
            ConfigDetails details = mapper.readValue(new File("properties.json"), ConfigDetails.class);
            System.out.println(details.getAppID());

            List entities = details.getEntities();
            for (Object entity : entities) {
                System.out.println(entity.toString());
            }
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

我得到的输出是

MyAppId
com.config.Entity@2096442d
com.config.Entity@9f70c54

这里不是打印可用的值，而是打印哈希码。请让我知道如何打印这些值。

谢谢

Answer 1

只需像这样访问 getter 方法 entity.getName() 并使用 Entity 而不是 Object:

MainClass obj = new MainClass();
    ObjectMapper mapper = new ObjectMapper();

    try {

        // Convert JSON string from file to Object
        ConfigDetails details = mapper.readValue(new File("properties.json"), ConfigDetails.class);
        System.out.println(details.getAppID());

        List entities = details.getEntities();
        for (Entity entity : entities) {
            System.out.println(entity.getName());
        }
    } catch (JsonGenerationException e) {
        e.printStackTrace();
    } catch (JsonMappingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }