改造转换问题 - 如何为具体 JSON 正确创建 POJO 类：

【问题标题】：Retrofit conversion issue - how to correctly create POJO class for concrete JSON:改造转换问题 - 如何为具体 JSON 正确创建 POJO 类：
【发布时间】：2019-06-09 15:56:57
【问题描述】：

我是 android 新手，正在构建一个使用 Retrofit 库从 REST API 加载数据的应用程序。我以前设法让它工作，但现在当我向我的 POJO 类添加更多变量时，Retrofit 似乎有转换问题。它转到“OnFailure”，错误不是 IOException 类型。我认为 Lecture 对象列表可能有问题。

这是源 JSON 的示例：

[  
   {  
      "id":1603,
      "date":"2018-09-11T22:12:59",
      "date_gmt":"2018-09-11T20:12:59",
      "guid":{  
         "rendered":"https:\/\/get-splashed.cz\/?p=1603"
      },
      "modified":"2018-09-11T22:22:01",
      "modified_gmt":"2018-09-11T20:22:01",
      "slug":"stein-and-meredith",
      "status":"publish",
      "type":"post",
      "link":"https:\/\/get-splashed.cz\/speakers\/stein-and-meredith",
      "title":{  
         "rendered":"Stein and Meredith"
      },
      "content":{  
         "rendered":"Animation and Games. Whatever your experience",
         "protected":false
      },
      "excerpt":{  
         "rendered":"Head of Compositing",
         "protected":false
      },
      "author":1,
      "featured_media":1606,
      "comment_status":"open",
      "ping_status":"open",
      "sticky":false,
      "template":"",
      "format":"standard",
      "meta":[  

      ],
      "categories":[  
         2
      ],
      "tags":[  

      ],
      "acf":{  
         "role":"",
         "job":"<b>Escape Studios<\/b>",
         "social":false,
         "speaker_slider_shortcode":"[rev_slider alias=\"escape\"]",
         "o_prednasce":[  
            {  
               "nazev_prednasky":"Creating a killer showreel: advice & tips for VFX, Animation & Games",
               "den_prednasky":"nedele",
               "cas_prednasky":"17:30",
               "typ":"P\u0159edn\u00e1\u0161ka",
               "misto_konani":"Main Hall",
               "doba_trvani":"60",
               "prave_probiha":""
            }
         ]
      }
   },
   {  
      "id":1452,
      "date":"2018-08-13T22:41:19",
      "date_gmt":"2018-08-13T20:41:19",
      "guid":{  
         "rendered":"https:\/\/get-splashed.cz\/?p=1452"
      },
      "modified":"2018-08-14T11:27:11",
      "modified_gmt":"2018-08-14T09:27:11",
      "slug":"jan-jinda",
      "status":"publish",
      "type":"post",
      "link":"https:\/\/get-splashed.cz\/speakers\/jan-jinda",
      "title":{  
         "rendered":"Jan Jinda"
      },
      "content":{  
         "rendered":"<p>Czech born London based 3D Generalist",
         "protected":false
      },
      "excerpt":{  
         "rendered":"Czech born London based",
         "protected":false
      },
      "author":1,
      "featured_media":1453,
      "comment_status":"open",
      "ping_status":"open",
      "sticky":false,
      "template":"",
      "format":"standard",
      "meta":[  

      ],
      "categories":[  
         2
      ],
      "tags":[  

      ],
      "acf":{  
         "role":"Senior Build TD",
         "job":"<b>Dneg<\/b>",
         "social":[  
            {  
               "odkaz":"https:\/\/www.facebook.com\/jan.jinda",
               "socialni_sit":"facebook"
            },
            {  
               "odkaz":"https:\/\/www.linkedin.com\/in\/janjinda\/",
               "socialni_sit":"linkedin"
            }
         ],
         "speaker_slider_shortcode":"[rev_slider alias=\"jinda\"]",
         "o_prednasce":[  
            {  
               "nazev_prednasky":"Building massive Jaegers for PR2",
               "den_prednasky":"sobota",
               "cas_prednasky":"15:00",
               "typ":"P\u0159edn\u00e1\u0161ka",
               "misto_konani":"Main Hall",
               "doba_trvani":"60",
               "prave_probiha":""
            }
         ]
      }
   }
]

还有我的 POJO 课：

import com.google.gson.annotations.SerializedName;

import java.util.List;

public class Speaker {

    @SerializedName("id")
    private int mId;

    @SerializedName("title")
    private Title mTitle;

    @SerializedName("acf")
    private Acf mAcf;

    @SerializedName("featured_media")
    private int mMediaId;

    @SerializedName("content")
    private Content mContent;

    String mImageUrl = "";

    // indicator if the speaker is fake - zig-zag layout
    private boolean mFakeSpeaker = false;

    public Speaker(int id, Title title, Acf acf, int mediaId, String imageUrl, boolean fakeSpeaker) {
        mId = id;
        mTitle = title;
        mAcf = acf;
        mImageUrl = imageUrl;
        mMediaId = mediaId;
        mFakeSpeaker = fakeSpeaker;
    }

    public int getId() {
        return mId;
    }

    public Title getTitle() {
        return mTitle;
    }

    public Acf getAcf() {
        return mAcf;
    }

    public int getMediaId() {
        return mMediaId;
    }

    public String getImageUrl() {
        return mImageUrl;
    }

    public void setImageUrl(String imageUrl) {
        mImageUrl = imageUrl;
    }

    public boolean getIsFakeSpeaker() {
        return mFakeSpeaker;
    }

    public void setIsFakeSpeaker(boolean isFakeSpeaker) {
        mFakeSpeaker = isFakeSpeaker;
    }

    public Content getContent() {
        return mContent;
    }

    public class Title {

        @SerializedName("rendered")
        private String mName;

        public Title(String name) {
            mName = name;
        }

        public String getName() {
            return mName;
        }
    }

    public class Acf {
        @SerializedName("role")
        private String mRole;

        @SerializedName("job")
        private String mCompany;

        @SerializedName("o_prednasce")
        private List<Lecture> mLectures;


        public Acf(String role, String company, List<Lecture> lectures) {
            mRole = role;
            mCompany = company;
            mLectures = lectures;
        }

        public String getRole() {
            return mRole;
        }

        public String getCompany() {
            return mCompany;
        }

        public List<Lecture> getLectures() {
            return mLectures;
        }

        public class Lecture {

            @SerializedName("nazev_prednasky")
            private String mLectureName;

            @SerializedName("den_prednasky")
            private String mLectureDay;

            @SerializedName("cas_prednasky")
            private String mLectureTime;

            public Lecture(String lectureName, String lectureDay, String lectureTime) {
                mLectureName = lectureName;
                mLectureDay = lectureDay;
                mLectureTime = lectureTime;
            }

            public String getLectureName() {
                return mLectureName;
            }

            public String getLectureDay() {
                return mLectureDay;
            }

            public String getLectureTime() {
                return mLectureTime;
            }
        }
    }

    public class Content {

        @SerializedName("rendered")
        private String mDescription;

        public Content(String description) {
            mDescription = description;
        }

        public String getDescription() {
            return mDescription;
        }
    }
}

在我添加 Lecture 类之前，代码一直有效。现在我无法弄清楚这里可能存在什么问题。

编辑：在 Retrofit 的 onFailure 方法中记录错误类型后：

            public void onFailure(Call<List<Speaker>> call, Throwable t) {

                if (t instanceof IOException) {
                    Log.v("RetrofitSplash", "No internet connection");
                } else {
                    Log.v("RetrofitSplash", "conversion issue! " + t.getMessage());
                }
            }

我发现有一个问题：“应为 BEGIN_ARRAY，但在第 1 行第 46857 列路径 $[10].acf.o_prednasce 为 BOOLEAN”

然后我再次查看 JSON，发现有一个字段“acf.o_prednasce”在一种情况下不是数组，而是“假”，即布尔值。

查看更大的 JSON 示例：

[  
   {  
      "id":1603,
      "date":"2018-09-11T22:12:59",
      "date_gmt":"2018-09-11T20:12:59",
      "guid":{  
         "rendered":"https:\/\/get-splashed.cz\/?p=1603"
      },
      "modified":"2018-09-11T22:22:01",
      "modified_gmt":"2018-09-11T20:22:01",
      "slug":"stein-and-meredith",
      "status":"publish",
      "type":"post",
      "link":"https:\/\/get-splashed.cz\/speakers\/stein-and-meredith",
      "title":{  
         "rendered":"Stein and Meredith"
      },
      "content":{  
         "rendered":"Animation and Games. Whatever your experience",
         "protected":false
      },
      "excerpt":{  
         "rendered":"Head of Compositing",
         "protected":false
      },
      "author":1,
      "featured_media":1606,
      "comment_status":"open",
      "ping_status":"open",
      "sticky":false,
      "template":"",
      "format":"standard",
      "meta":[  

      ],
      "categories":[  
         2
      ],
      "tags":[  

      ],
      "acf":{  
         "role":"",
         "job":"<b>Escape Studios<\/b>",
         "social":false,
         "speaker_slider_shortcode":"[rev_slider alias=\"escape\"]",
         "o_prednasce":[  
            {  
               "nazev_prednasky":"Creating a killer showreel: advice & tips for VFX, Animation & Games",
               "den_prednasky":"nedele",
               "cas_prednasky":"17:30",
               "typ":"P\u0159edn\u00e1\u0161ka",
               "misto_konani":"Main Hall",
               "doba_trvani":"60",
               "prave_probiha":""
            }
         ]
      }
   },
   {  
      "id":1452,
      "date":"2018-08-13T22:41:19",
      "date_gmt":"2018-08-13T20:41:19",
      "guid":{  
         "rendered":"https:\/\/get-splashed.cz\/?p=1452"
      },
      "modified":"2018-08-14T11:27:11",
      "modified_gmt":"2018-08-14T09:27:11",
      "slug":"jan-jinda",
      "status":"publish",
      "type":"post",
      "link":"https:\/\/get-splashed.cz\/speakers\/jan-jinda",
      "title":{  
         "rendered":"Jan Jinda"
      },
      "content":{  
         "rendered":"<p>Czech born London based 3D Generalist",
         "protected":false
      },
      "excerpt":{  
         "rendered":"Czech born London based",
         "protected":false
      },
      "author":1,
      "featured_media":1453,
      "comment_status":"open",
      "ping_status":"open",
      "sticky":false,
      "template":"",
      "format":"standard",
      "meta":[  

      ],
      "categories":[  
         2
      ],
      "tags":[  

      ],
      "acf":{  
         "role":"Senior Build TD",
         "job":"<b>Dneg<\/b>",
         "social":[  
            {  
               "odkaz":"https:\/\/www.facebook.com\/jan.jinda",
               "socialni_sit":"facebook"
            },
            {  
               "odkaz":"https:\/\/www.linkedin.com\/in\/janjinda\/",
               "socialni_sit":"linkedin"
            }
         ],
         "speaker_slider_shortcode":"[rev_slider alias=\"jinda\"]",
         "o_prednasce":[  
            {  
               "nazev_prednasky":"Building massive Jaegers for PR2",
               "den_prednasky":"sobota",
               "cas_prednasky":"15:00",
               "typ":"P\u0159edn\u00e1\u0161ka",
               "misto_konani":"Main Hall",
               "doba_trvani":"60",
               "prave_probiha":""
            }
         ]
      }
   },
  {  
      "id":855,
      "date":"2018-05-02T23:21:11",
      "date_gmt":"2018-05-02T21:21:11",
      "guid":{  
         "rendered":"http:\/\/get-splashed.cz\/?p=855"
      },
      "modified":"2018-09-14T22:15:38",
      "modified_gmt":"2018-09-14T20:15:38",
      "slug":"talk-info-will-be-soon",
      "status":"publish",
      "type":"post",
      "link":"https:\/\/get-splashed.cz\/nezarazene\/talk-info-will-be-soon",
      "title":{  
         "rendered":"Speaker soon"
      },
      "content":{  
         "rendered":"",
         "protected":false
      },
      "excerpt":{  
         "rendered":"",
         "protected":false
      },
      "author":1,
      "featured_media":863,
      "comment_status":"open",
      "ping_status":"open",
      "sticky":false,
      "template":"",
      "format":"standard",
      "meta":[  

      ],
      "categories":[  
         1
      ],
      "tags":[  

      ],
      "acf":{  
         "role":"",
         "job":"",
         "social":false,
         "speaker_slider_shortcode":"",
         "o_prednasce":false
      }
   }
]

【问题讨论】：

    标签： java android retrofit2 pojo


    【解决方案1】：

    最后我自己找到了解决方案：由于 JSON 中的字段“acf.o_prednasce”在一种情况下是布尔值，而在其他情况下是一个数组，我通过字段“类别”过滤 API 响应以获得一个在一个响应中输入此字段的类型。

    【讨论】：

      【解决方案2】：

      不需要默认构造函数；就像那些 @Expose 不需要注解一样。

      尝试使用ArrayList&lt;Lecture&gt; 而不是List&lt;Lecture&gt;。

      【讨论】：

      • 不，将 List 更改为 ArrayList 没有帮助，问题仍然存在。但是感谢您查看代码。
      【解决方案3】：

      序列化程序通常要求对象具有默认构造函数。

      为 Lecture 添加一个默认构造函数，看看会发生什么。

      【讨论】：

      • 不，即使向 Lecture 类添加默认构造函数也无济于事:(
      【解决方案4】：

      试试这个 www.jsonschema2pojo.org

      -----------------------------------com.example.Acf.java-----------------------------------

package com.example;

import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Acf {

@SerializedName("role")
@Expose
private String role;
@SerializedName("job")
@Expose
private String job;
@SerializedName("social")
@Expose
private List<Social> social = null;
@SerializedName("speaker_slider_shortcode")
@Expose
private String speakerSliderShortcode;
@SerializedName("o_prednasce")
@Expose
private List<OPrednasce> oPrednasce = null;

public String getRole() {
return role;
}

public void setRole(String role) {
this.role = role;
}

public String getJob() {
return job;
}

public void setJob(String job) {
this.job = job;
}

public List<Social> getSocial() {
return social;
}

public void setSocial(List<Social> social) {
this.social = social;
}

public String getSpeakerSliderShortcode() {
return speakerSliderShortcode;
}

public void setSpeakerSliderShortcode(String speakerSliderShortcode) {
this.speakerSliderShortcode = speakerSliderShortcode;
}

public List<OPrednasce> getOPrednasce() {
return oPrednasce;
}

public void setOPrednasce(List<OPrednasce> oPrednasce) {
this.oPrednasce = oPrednasce;
}

}
-----------------------------------com.example.Content.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Content {

@SerializedName("rendered")
@Expose
private String rendered;
@SerializedName("protected")
@Expose
private Boolean _protected;

public String getRendered() {
return rendered;
}

public void setRendered(String rendered) {
this.rendered = rendered;
}

public Boolean getProtected() {
return _protected;
}

public void setProtected(Boolean _protected) {
this._protected = _protected;
}

}
-----------------------------------com.example.Example.java-----------------------------------

package com.example;

import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Example {

@SerializedName("id")
@Expose
private Integer id;
@SerializedName("date")
@Expose
private String date;
@SerializedName("date_gmt")
@Expose
private String dateGmt;
@SerializedName("guid")
@Expose
private Guid guid;
@SerializedName("modified")
@Expose
private String modified;
@SerializedName("modified_gmt")
@Expose
private String modifiedGmt;
@SerializedName("slug")
@Expose
private String slug;
@SerializedName("status")
@Expose
private String status;
@SerializedName("type")
@Expose
private String type;
@SerializedName("link")
@Expose
private String link;
@SerializedName("title")
@Expose
private Title title;
@SerializedName("content")
@Expose
private Content content;
@SerializedName("excerpt")
@Expose
private Excerpt excerpt;
@SerializedName("author")
@Expose
private Integer author;
@SerializedName("featured_media")
@Expose
private Integer featuredMedia;
@SerializedName("comment_status")
@Expose
private String commentStatus;
@SerializedName("ping_status")
@Expose
private String pingStatus;
@SerializedName("sticky")
@Expose
private Boolean sticky;
@SerializedName("template")
@Expose
private String template;
@SerializedName("format")
@Expose
private String format;
@SerializedName("meta")
@Expose
private List<Object> meta = null;
@SerializedName("categories")
@Expose
private List<Integer> categories = null;
@SerializedName("tags")
@Expose
private List<Object> tags = null;
@SerializedName("acf")
@Expose
private Acf acf;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getDate() {
return date;
}

public void setDate(String date) {
this.date = date;
}

public String getDateGmt() {
return dateGmt;
}

public void setDateGmt(String dateGmt) {
this.dateGmt = dateGmt;
}

public Guid getGuid() {
return guid;
}

public void setGuid(Guid guid) {
this.guid = guid;
}

public String getModified() {
return modified;
}

public void setModified(String modified) {
this.modified = modified;
}

public String getModifiedGmt() {
return modifiedGmt;
}

public void setModifiedGmt(String modifiedGmt) {
this.modifiedGmt = modifiedGmt;
}

public String getSlug() {
return slug;
}

public void setSlug(String slug) {
this.slug = slug;
}

public String getStatus() {
return status;
}

public void setStatus(String status) {
this.status = status;
}

public String getType() {
return type;
}

public void setType(String type) {
this.type = type;
}

public String getLink() {
return link;
}

public void setLink(String link) {
this.link = link;
}

public Title getTitle() {
return title;
}

public void setTitle(Title title) {
this.title = title;
}

public Content getContent() {
return content;
}

public void setContent(Content content) {
this.content = content;
}

public Excerpt getExcerpt() {
return excerpt;
}

public void setExcerpt(Excerpt excerpt) {
this.excerpt = excerpt;
}

public Integer getAuthor() {
return author;
}

public void setAuthor(Integer author) {
this.author = author;
}

public Integer getFeaturedMedia() {
return featuredMedia;
}

public void setFeaturedMedia(Integer featuredMedia) {
this.featuredMedia = featuredMedia;
}

public String getCommentStatus() {
return commentStatus;
}

public void setCommentStatus(String commentStatus) {
this.commentStatus = commentStatus;
}

public String getPingStatus() {
return pingStatus;
}

public void setPingStatus(String pingStatus) {
this.pingStatus = pingStatus;
}

public Boolean getSticky() {
return sticky;
}

public void setSticky(Boolean sticky) {
this.sticky = sticky;
}

public String getTemplate() {
return template;
}

public void setTemplate(String template) {
this.template = template;
}

public String getFormat() {
return format;
}

public void setFormat(String format) {
this.format = format;
}

public List<Object> getMeta() {
return meta;
}

public void setMeta(List<Object> meta) {
this.meta = meta;
}

public List<Integer> getCategories() {
return categories;
}

public void setCategories(List<Integer> categories) {
this.categories = categories;
}

public List<Object> getTags() {
return tags;
}

public void setTags(List<Object> tags) {
this.tags = tags;
}

public Acf getAcf() {
return acf;
}

public void setAcf(Acf acf) {
this.acf = acf;
}

}
-----------------------------------com.example.Excerpt.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Excerpt {

@SerializedName("rendered")
@Expose
private String rendered;
@SerializedName("protected")
@Expose
private Boolean _protected;

public String getRendered() {
return rendered;
}

public void setRendered(String rendered) {
this.rendered = rendered;
}

public Boolean getProtected() {
return _protected;
}

public void setProtected(Boolean _protected) {
this._protected = _protected;
}

}
-----------------------------------com.example.Guid.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Guid {

@SerializedName("rendered")
@Expose
private String rendered;

public String getRendered() {
return rendered;
}

public void setRendered(String rendered) {
this.rendered = rendered;
}

}
-----------------------------------com.example.OPrednasce.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class OPrednasce {

@SerializedName("nazev_prednasky")
@Expose
private String nazevPrednasky;
@SerializedName("den_prednasky")
@Expose
private String denPrednasky;
@SerializedName("cas_prednasky")
@Expose
private String casPrednasky;
@SerializedName("typ")
@Expose
private String typ;
@SerializedName("misto_konani")
@Expose
private String mistoKonani;
@SerializedName("doba_trvani")
@Expose
private String dobaTrvani;
@SerializedName("prave_probiha")
@Expose
private String praveProbiha;

public String getNazevPrednasky() {
return nazevPrednasky;
}

public void setNazevPrednasky(String nazevPrednasky) {
this.nazevPrednasky = nazevPrednasky;
}

public String getDenPrednasky() {
return denPrednasky;
}

public void setDenPrednasky(String denPrednasky) {
this.denPrednasky = denPrednasky;
}

public String getCasPrednasky() {
return casPrednasky;
}

public void setCasPrednasky(String casPrednasky) {
this.casPrednasky = casPrednasky;
}

public String getTyp() {
return typ;
}

public void setTyp(String typ) {
this.typ = typ;
}

public String getMistoKonani() {
return mistoKonani;
}

public void setMistoKonani(String mistoKonani) {
this.mistoKonani = mistoKonani;
}

public String getDobaTrvani() {
return dobaTrvani;
}

public void setDobaTrvani(String dobaTrvani) {
this.dobaTrvani = dobaTrvani;
}

public String getPraveProbiha() {
return praveProbiha;
}

public void setPraveProbiha(String praveProbiha) {
this.praveProbiha = praveProbiha;
}

}
-----------------------------------com.example.Social.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Social {

@SerializedName("odkaz")
@Expose
private String odkaz;
@SerializedName("socialni_sit")
@Expose
private String socialniSit;

public String getOdkaz() {
return odkaz;
}

public void setOdkaz(String odkaz) {
this.odkaz = odkaz;
}

public String getSocialniSit() {
return socialniSit;
}

public void setSocialniSit(String socialniSit) {
this.socialniSit = socialniSit;
}

}
-----------------------------------com.example.Title.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Title {

@SerializedName("rendered")
@Expose
private String rendered;

public String getRendered() {
return rendered;
}

public void setRendered(String rendered) {
this.rendered = rendered;
}

}

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