嘗試使用MVC模式讀取Java中的json檔案時出現問題

我正在嘗試使用 MVC 模式和 json.simple 庫從 JAVA 中的 JSONArray 列印一些 JSONObject，但是當我運行它時，程式只列印最后一個 JSONObject。

這是我的主要課程：

package Main;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

import Controlador.Controlador;
import Vista.Vista;
import Modelo.Modelo;

public class Main {

    private static String ID;

    public static void main(String[] args) throws IOException, InterruptedException {

        Modelo modelo = llenarDatosModelo();
        Vista vista = new Vista();
        
        //se crea un objeto controlador y se le pasa el modelo y la vista
        
        Controlador controlador = new Controlador(modelo, vista);
        
        // se muestra los datos
        
        controlador.actualizarVista();
    }


    //método estático que retorna el autor con sus datos
    
    private static Modelo llenarDatosModelo() {
        
        JSONParser jsonParser = new JSONParser ();
        
        try(FileReader reader = new FileReader ("datos.json")) {
            
            JSONObject documento = (JSONObject) jsonParser.parse(reader);
    
            JSONObject resultados = (JSONObject)documento.get("search-results");
            
            JSONArray Entrys = (JSONArray) resultados.get("entry");
            for(Object Entry: Entrys) {
                mostrarInformacionEntry ((JSONObject) Entry);
            }       
            
        } catch (FileNotFoundException e) {
        e.printStackTrace();    
        } catch(IOException e) {
            e.printStackTrace();        
        } catch(ParseException e) {
            e.printStackTrace();
        }
        
        Modelo autor = new Modelo();
        autor.setID(ID);
        return autor;
    }


    private static void mostrarInformacionEntry(JSONObject entry) {
        
        ID = (String) entry.get("dc:identifier");
        
    }   

這是我的模型：

package Modelo;

public class Modelo {   
    
    private String ID;
    private String url;
    private String eid;
    private String document_count;
    private String cited_by_count;
    private String citation_count;
    private String affiliation;
    private String give_name;
    private String classification;
    private String publication_start;
    private String publication_end;
    
    public Modelo() {
    }
    
    public String getID() {
        return ID;
    }
    public void setID(String string) {
        this.ID = string;
    }
    
    public String geturl() {
        return url;
    }
    public void seturl(String url) {
        this.url = url;
    }
    
    public String geteid() {
        return eid;
    }
    public void seteid(String eid) {
        this.eid = eid;
    }
    
    public String getdocument_count() {
        return document_count;
    }
    public void setdocument_count(String document_count) {
        this.document_count = document_count;
    }
    
    public String getcited_by_count() {
        return cited_by_count;
    }
    public void setcited_by_count(String cited_by_count) {
        this.cited_by_count = cited_by_count;
    }
    
    public String getcitation_count() {
        return citation_count;
    }
    public void setcitation_count(String citation_count) {
        this.citation_count = citation_count;
    }
    
    public String getaffiliation() {
        return affiliation;
    }
    public void setaffiliation(String affiliation) {
        this.affiliation = affiliation;
    }
    
    public String getgive_name() {
        return give_name;
    }
    public void setgive_name(String give_name) {
        this.give_name = give_name;
    }
    
    public String getclassification() {
        return classification;
    }
    public void setclassification(String classification) {
        this.classification = classification;
    }
    
    public String getpublication_start() {
        return publication_start;
    }
    public void setpublication_start(String publication_start) {
        this.publication_start = publication_start;
    }
    
    public String getpublication_end() {
        return publication_end;
    }
    public void setpublication_end(String publication_end) {
        this.publication_end = publication_end;
    }
    
}

這是我的觀點：

package Vista;

public class Vista {
    
    public void imprimirDatos(String string,String url, String eid, String document_count, String cited_by_count, String citation_count, String affiliation, String give_name, String classification, String publication_start, String publication_end) {

        System.out.println("\n****AUTOR****");
        System.out.println("ID: " string);
        System.out.println("url: " url);
        System.out.println("eid: " eid);
        System.out.println("document_count: " document_count);
        System.out.println("cited_by_count: " cited_by_count);
        System.out.println("citation_count: " citation_count);
        System.out.println("affiliation: " affiliation);
        System.out.println("give_name: " give_name);
        System.out.println("classification: " classification);
        System.out.println("publication_start: " publication_start);
        System.out.println("publication_end: " publication_end);
    }

}

這是我的控制器：

package Controlador;

import Modelo.Modelo;
import Vista.Vista;

public class Controlador {
    
    //objetos vista y modelo
    
    private Vista vista;
    private Modelo modelo;
    
    //constructor para inicializar el modelo y la vista
    
    public Controlador(Modelo modelo, Vista vista) {
        this.modelo = modelo;
        this.vista = vista;
    }
    
    //getters y setters para el modelo
    
    public String getID() {
        return modelo.getID();
    }
    public void setID(String ID) {
        this.modelo.setID(ID);
    }
    
    public String geturl() {
        return modelo.geturl();
    }
    public void seturl(String url) {
        this.modelo.seturl(url); 
    }
    
    public String geteid() {
        return modelo.geteid();
    }
    public void seteid(String eid) {
        this.modelo.seteid(eid); 
    }
    
    public String getdocument_count() {
        return modelo.getdocument_count();
    }
    public void setdocument_count(String document_count) {
        this.modelo.setdocument_count(document_count);
    }
    
    public String getcited_by_count() {
        return modelo.getcited_by_count();
    }
    public void setcited_by_count(String cited_by_count) {
        this.modelo.setcited_by_count(cited_by_count);
    }
    
    public String getcitation_count() {
        return modelo.getcitation_count();
    }
    public void setcitation_count(String citation_count) {
        this.modelo.setcitation_count(citation_count);
    }
    
    public String getaffiliation() {
        return modelo.getaffiliation();
    }
    public void setaffiliation(String affiliation) {
        this.modelo.setaffiliation(affiliation );
    }
    
    public String getgive_name() {
        return modelo.getgive_name();
    }
    public void setgive_name(String give_name) {
        this.modelo.setgive_name(give_name); 
    }
    
    public String getclassification() {
        return modelo.getclassification();
    }
    public void setclassification(String classification) {
        this.modelo.setclassification(classification); 
    }
    
    public String getpublication_start() {
        return modelo.getpublication_start();
    }
    public void setpublication_start(String publication_start) {
        this.modelo.setpublication_start(publication_start); 
    }
    
    public String getpublication_end() {
        return modelo.getpublication_end();
    }
    public void setpublication_end(String publication_end) {
        this.modelo.setpublication_end(publication_end); 
    }
    
    //pasa el modelo a la vista para presentar los datos
    public void actualizarVista() {
        
        vista.imprimirDatos(modelo.getID(),modelo.geturl(), modelo.geteid(), modelo.getdocument_count(), modelo.getcited_by_count(), modelo.getcitation_count(), modelo.getaffiliation(), modelo.getgive_name(), modelo.getclassification(), modelo.getpublication_start(), modelo.getpublication_end());
    }

}

當我運行它時，控制臺會顯示：

****AUTOR****
ID: SCOPUS_ID:85137292444
url: null
eid: null
document_count: null
cited_by_count: null
citation_count: null
affiliation: null

JSONArray 條目有多篇文章，我希望程式將它們全部列印出來。有誰知道我做錯了什么？

JSON檔案是：

https://drive.google.com/file/d/1t53qiU64eJVUupDA-Ie2ZR1Xakz7npGI/view?usp=sharing

uj5u.com熱心網友回復：

您的方法mostrarInformacionEntry是讀取一個 JSON 陣列條目的欄位。您的問題是，此方法不會為每個條目創建一個新模型。相反，它將讀取的值分配給dc:identifier類變數ID。這是針對陣列中的所有條目完成的。一個條目會覆寫前一個條目的已保存 ID。最后，您使用最后加載的條目的 ID 創建一個模型。但是您應該為每個條目創建一個模型。

您需要一個自定義條目類/POJO：

public class ModeloEntry {   
    
    private String ID;
    private String url;
    private String eid;
    private String document_count;
    private String cited_by_count;
    private String citation_count;
    private String affiliation;
    private String give_name;
    private String classification;
    private String publication_start;
    private String publication_end;
    
    public ModeloEntry() {
    }
    
    public String getID() {
        return ID;
    }
    public void setID(String string) {
        this.ID = string;
    }
    
    public String geturl() {
        return url;
    }
    public void seturl(String url) {
        this.url = url;
    }
    
    public String geteid() {
        return eid;
    }
    public void seteid(String eid) {
        this.eid = eid;
    }
    
    public String getdocument_count() {
        return document_count;
    }
    public void setdocument_count(String document_count) {
        this.document_count = document_count;
    }
    
    public String getcited_by_count() {
        return cited_by_count;
    }
    public void setcited_by_count(String cited_by_count) {
        this.cited_by_count = cited_by_count;
    }
    
    public String getcitation_count() {
        return citation_count;
    }
    public void setcitation_count(String citation_count) {
        this.citation_count = citation_count;
    }
    
    public String getaffiliation() {
        return affiliation;
    }
    public void setaffiliation(String affiliation) {
        this.affiliation = affiliation;
    }
    
    public String getgive_name() {
        return give_name;
    }
    public void setgive_name(String give_name) {
        this.give_name = give_name;
    }
    
    public String getclassification() {
        return classification;
    }
    public void setclassification(String classification) {
        this.classification = classification;
    }
    
    public String getpublication_start() {
        return publication_start;
    }
    public void setpublication_start(String publication_start) {
        this.publication_start = publication_start;
    }
    
    public String getpublication_end() {
        return publication_end;
    }
    public void setpublication_end(String publication_end) {
        this.publication_end = publication_end;
    }
    
}

你需要一個 MVC 背景關系中的模型，包含所有條目：

public class Modelo {
    private List<ModeloEntry> entries = new ArrayList<>();

    public void addEntry(ModeloEntry entry) {
        this.entries.add(entry);
    }

    public List<ModeloEntry> getEntries() {
        return entries;
    }
}

然后您可以執行以下操作：

public class Main() {
    // ...

    private static Modelo llenarDatosModelo() {
        
        Modelo autor = new Modelo(); // Create the MVC model first
        JSONParser jsonParser = new JSONParser ();
        
        try(FileReader reader = new FileReader ("datos.json")) {
            
            JSONObject documento = (JSONObject) jsonParser.parse(reader);
    
            JSONObject resultados = (JSONObject)documento.get("search-results");
            
            JSONArray Entrys = (JSONArray) resultados.get("entry");
            for(Object Entry: Entrys) {
                ModeloEntry entry = mostrarInformacionEntry ((JSONObject) Entry); // Create a entry instance per JSON array entry
                author.addEntry(entry); // Add the entry to your MVC model
            }       
            
        } catch (FileNotFoundException e) {
        e.printStackTrace();    
        } catch(IOException e) {
            e.printStackTrace();        
        } catch(ParseException e) {
            e.printStackTrace();
        }
        
        return autor; // Return your MVC model
    }

    private static ModeloEntry mostrarInformacionEntry(JSONObject entry) {
        
        ModeloEntry entry = new ModeloEntry(); // Create a entry instance
        entry.setId((String) entry.get("dc:identifier"));
        return entry;
    } 
}

然后將您的 for-each 回圈外包給您的控制器類：

public class Controlador {
    private Vista vista;
    private Modelo modelo;

    public void actualizarVista() {
        
        // Print each entry of your MVC model line by line
        for(ModeloEntry entry : modelo.getEntries()) {
            vista.imprimirDatos(modelo.getID(),modelo.geturl(), modelo.geteid(), modelo.getdocument_count(), modelo.getcited_by_count(), modelo.getcitation_count(), modelo.getaffiliation(), modelo.getgive_name(), modelo.getclassification(), modelo.getpublication_start(), modelo.getpublication_end());
        }
    }
}

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