How to get page size of pdf document iText 7

I have a java program in iText 7 that receive JSON data and generate a PDF document (with header and footer) that works fine with data in variable clientData in comment, but when use the variable in no comments clientData doesn’t works, i’m getting this error java.lang.NullPointerException, the error appears when build the header and footer (in this line Rectangle pageSize = document.getPdfDocument().getPage(i).getPageSize();), but don’t know what data is null, because the JSON data and the structure of the PDF is the same, what am i doing wrong?

This is all the code:

import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfPage;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.kernel.pdf.extgstate.PdfExtGState;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Table;
import com.itextpdf.layout.element.Text;
import com.itextpdf.io.image.ImageData;
import com.itextpdf.io.image.ImageDataFactory;
import com.itextpdf.kernel.colors.Color;
import com.itextpdf.kernel.colors.DeviceRgb;
import com.itextpdf.kernel.font.PdfFont;
import com.itextpdf.kernel.font.PdfFontFactory;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.layout.element.Cell;
import com.itextpdf.layout.element.Image;
import com.itextpdf.layout.element.List;
import com.itextpdf.layout.element.ListItem;
import com.itextpdf.layout.element.Paragraph;
import com.itextpdf.layout.property.TextAlignment;
import com.itextpdf.layout.property.VerticalAlignment;
import java.io.File;
import java.io.IOException;
import java.text.NumberFormat;
import java.util.Locale;

import org.json.JSONArray;
import org.json.JSONObject;

public class PDFGenerator {
public static final String DESTINATION = "path/exampleSMA.pdf";

public static void main(String[] args) throws Exception {
    File file = new File(DEST);
    file.getParentFile().mkdirs();
    //WORK
    //String clientData = "'{"nombre_cliente":"Postobon","contacto":"Kelly Paz","email":"[e-mail]","telefono":"233774983","observaciones":"","totalizar":true,"mostrar_impuesto":false,"credito":true,"creador":"jplata","creador_nombre":"JAIME ANTONIO","creador_apellido":"PLATA BOGOYA","cargo_asesor":"GERENTE","email_asesor":"[e-mail]","productos":[{"modelo":"BOLSA ACCESORIOS ESTANDAR","tela":"KAMBREL O POLITEX DE 70GR","cantidad":"3000","destino":186,"destino_label":"CALDAS - NEIRA","ancho":22,"alto":33,"fuelle":0,"manija":0,"estampado_cara_frontal":"1 TINTA MATE","estampado_cara_posterior":"2 TINTAS MATE","valor_bolsa":"1605","valor_iva":"304","iva":19,"accesorios_modelo":[{"id":"1","nombre":"CORDON ESTANDAR SENCILLO; PARA BOLSAS CIERRE CORDON O BOLERO.","ancho":0,"alto":0}],"accesorios_adicionales":[{"id":"37","nombre":"ESTE ACCESORIO SE USA PARA COLOCARLE BASE DE CARTON FORRADA EN EL MISMO MATERIAL A LA BOLSA. NORMALMENTE SE USA PARA LA BOLSA ANCHETA; PERO SE LE PUEDE COLOCAR A CUALQUIER BOLSA.","ancho":0,"alto":0},{"id":"23","nombre":"BOLSILLO EN EL MISMO MATERIAL DE LA BOLSA; SE USA PARA LA BOLSA AUTOGUARDABLE TIPO BILLETERA; O PARA CUALQUIER BOLSA QUE SE DESEE LLEVE UN BOLSILLO.  EN LOS CAMPOS ALTO Y ANCHO; INDIQUE LAS DIMENSIONES DE ÉSTE BOLSILLO.","ancho":20,"alto":20},{"id":"36","nombre":"ESTE ACCESORIO ES UNA CAPA QUE SE COLOCA ENCIMA DEL CUBREVESTIDO. EN EL CAMPO ALTO: INDIQUE EL ALTO DE LA CAPERUZA.","ancho":0,"alto":22}],"cantidadesReporte":[{"cantidad":3000,"valor_bolsa":1605,"valor_iva":0,"subtotal":4815000,"total":4815000}]}]}'";
    //NOT WORK
    String clientData = "'{"nombre_cliente":"MARCA DE PRUEBA","contacto":"Harry","email":"[e-mail]","telefono":"4553773773","observaciones":"","totalizar":false,"mostrar_impuesto":true,"credito":false,"creador":"jvalderrama","creador_nombre":"JUAN CARLOS","creador_apellido":"VALDERRAMA GONZALEZ","cargo_asesor":"desarrollador","email_asesor":"[e-mail]","telefono_asesor":"2373719 EXT 1147 - 5138731 - 8033205","celular_asesor":"3149008989","productos":[{"modelo":"BOLSA ACCESORIOS CIERRE ESPECIAL","tela":"KAMBREL O POLITEX DE 70GR","cantidad":"300,600,1000","destino":4,"destino_label":"ANTIOQUIA - BARBOSA","ancho":23,"alto":44,"fuelle":0,"manija":0,"estampado_cara_frontal":"1 TINTA MATE","estampado_cara_posterior":"SIN ESTAMPADO","estampado_fuelle_izquierdo":"SIN ESTAMPADO","estampado_fuelle_derecho":"SIN ESTAMPADO","estampado_fuelle_base":"SIN ESTAMPADO","valor_bolsa":"1543,1202,1151","valor_iva":"293,228,218","iva":19,"accesorios_modelo":[],"accesorios_adicionales":[{"id":"37","nombre":"BASE DE CARTON FORRADO","descripcion":"ESTE ACCESORIO SE USA PARA COLOCARLE BASE DE CARTON FORRADA EN EL MISMO MATERIAL A LA BOLSA. NORMALMENTE SE USA PARA LA BOLSA ANCHETA,PERO SE LE PUEDE COLOCAR A CUALQUIER BOLSA.","ancho":2,"alto":0}],"cantidadesReporte":[{"cantidad":300,"valor_bolsa":1543,"valor_iva":87900,"subtotal":462900,"total":550800},{"cantidad":600,"valor_bolsa":1202,"valor_iva":136800,"subtotal":721200,"total":858000},{"cantidad":1000,"valor_bolsa":1151,"valor_iva":218000,"subtotal":1151000,"total":1369000}]},{"modelo":"BOLSA ACCESORIOS CIERRE ESPECIAL","tela":"YUTE LAMINADO COLOR CRUDO","cantidad":"300,600,1000","destino":4,"destino_label":"ANTIOQUIA - BARBOSA","ancho":23,"alto":44,"fuelle":0,"manija":0,"estampado_cara_frontal":"1 TINTA MATE","estampado_cara_posterior":"SIN ESTAMPADO","estampado_fuelle_izquierdo":"SIN ESTAMPADO","estampado_fuelle_derecho":"SIN ESTAMPADO","estampado_fuelle_base":"SIN ESTAMPADO","valor_bolsa":"6439,5016,4830","valor_iva":"1223,953,917","iva":19,"accesorios_modelo":[],"accesorios_adicionales":[{"id":"37","nombre":"BASE DE CARTON FORRADO","descripcion":"ESTE ACCESORIO SE USA PARA COLOCARLE BASE DE CARTON FORRADA EN EL MISMO MATERIAL A LA BOLSA. NORMALMENTE SE USA PARA LA BOLSA ANCHETA,PERO SE LE PUEDE COLOCAR A CUALQUIER BOLSA.","ancho":2,"alto":0}],"cantidadesReporte":[{"cantidad":300,"valor_bolsa":6439,"valor_iva":366900,"subtotal":1931700,"total":2298600},{"cantidad":600,"valor_bolsa":5016,"valor_iva":571800,"subtotal":3009600,"total":3581400},{"cantidad":1000,"valor_bolsa":4830,"valor_iva":917000,"subtotal":4830000,"total":5747000}]},{"modelo":"BOLSA ACCESORIOS CIERRE ESPECIAL","tela":"TELA DE SUBLIMAR EN KAMB. DE 70GR","cantidad":"300,600,1000","destino":4,"destino_label":"ANTIOQUIA - BARBOSA","ancho":23,"alto":44,"fuelle":0,"manija":0,"estampado_cara_frontal":"1 TINTA MATE","estampado_cara_posterior":"SIN ESTAMPADO","estampado_fuelle_izquierdo":"SIN ESTAMPADO","estampado_fuelle_derecho":"SIN ESTAMPADO","estampado_fuelle_base":"SIN ESTAMPADO","valor_bolsa":"1906,1485,1423","valor_iva":"362,282,270","iva":19,"accesorios_modelo":[],"accesorios_adicionales":[{"id":"37","nombre":"BASE DE CARTON FORRADO","descripcion":"ESTE ACCESORIO SE USA PARA COLOCARLE BASE DE CARTON FORRADA EN EL MISMO MATERIAL A LA BOLSA. NORMALMENTE SE USA PARA LA BOLSA ANCHETA,PERO SE LE PUEDE COLOCAR A CUALQUIER BOLSA.","ancho":2,"alto":0}],"cantidadesReporte":[{"cantidad":300,"valor_bolsa":1906,"valor_iva":108600,"subtotal":571800,"total":680400},{"cantidad":600,"valor_bolsa":1485,"valor_iva":169200,"subtotal":891000,"total":1060200},{"cantidad":1000,"valor_bolsa":1423,"valor_iva":270000,"subtotal":1423000,"total":1693000}]}]}'";

    new PDFGenerator().createPdf(DEST, clientData);     
}

public void createPdf(String dest, String data) throws IOException {

    data = data.replace("'","");
    JSONObject jsonPeticion = new JSONObject(data);
    JSONArray jsonProductos= jsonPeticion.getJSONArray("productos");
    boolean mostrarIva = jsonPeticion.getBoolean("mostrar_impuesto");
    NumberFormat formateador = NumberFormat.getInstance(new Locale("us", "US"));
    formateador.setMinimumFractionDigits(0);
    formateador.setMaximumFractionDigits(0);
    System.out.println("JSON ARRAY......" + jsonProductos);
    System.out.println("JSON ARRAY LENGTH......" + jsonProductos.length());

    PdfDocument pdf = new PdfDocument(new PdfWriter(dest));
    try (Document document = new Document(pdf)) {

        document.setMargins(120, 36, 120, 36);

        document.add(new Paragraph("ESPECIFICACIONES TÉCNICAS DEL PRODUCTO")
                .setTextAlignment(TextAlignment.CENTER)
                .setBold());

        for (int i = 0; i < jsonProductos.length(); i++) {

        Text textoTinta = new Text("Tinta Utilizada");
        textoTinta.setUnderline(1.5f, -1);
        textoTinta.setTextAlignment(TextAlignment.LEFT);

        Text textoTintaDescripcion = new Text(": Las tintas que usamos son 100% Ecológicas y Base Agua, "
                + "nuestra visión no es solo comercial sino de responsabilidad "
                + "con el medio ambiente y social.");

        Text textoNota = new Text("NOTA: ").setBold();
        textoNota.setTextAlignment(TextAlignment.LEFT);

        Text textoNotaDescripcion = new Text("Señor cliente por favor tener presente, que en el momento "
                + "de la facturación, debemos facturar todo lo que salga, normalmente "
                + "puede salir un 5% de más o de menos.");

        document.add(new Paragraph(textoTinta).add(textoTintaDescripcion)
                .setTextAlignment(TextAlignment.JUSTIFIED));

        document.add(new Paragraph(textoNota).add(textoNotaDescripcion)
                .setTextAlignment(TextAlignment.JUSTIFIED));

        String IMG = "C:\path\images\logoSmallBiobolsa.png";
        String FONT = "C:\path\COMIC.ttf";
        ImageData imageData = ImageDataFactory.create(IMG);
        Image pdfImg = new Image(imageData);
        pdfImg.setWidth(70);
        pdfImg.setHeight(77);

        Color verdeBioBolsa = new DeviceRgb(5, 94, 27);
        PdfFont comic = PdfFontFactory.createFont(FONT, true);
        System.out.println("MARGENES SUPERIOR..... " + document.getTopMargin());
        System.out.println("MARGENES INFERIOR..... " + document.getBottomMargin());
        System.out.println("MARGENES IZQUIERDO..... " + document.getLeftMargin());
        System.out.println("MARGENES DERECHO..... " + document.getRightMargin());

        Paragraph headerImg = new Paragraph("").add(pdfImg);

        Paragraph headerNombreEmpresa = new Paragraph("BIO BOLSA S.A.S")
                .setFont(comic)
                .setFontSize(20)
                .setBold()
                .setFontColor(verdeBioBolsa);

        Paragraph headerSlogan = new Paragraph("!!Una Empresa con Conciencia Ambiental!!")
                .setFont(comic)
                .setFontSize(14)
                .setFontColor(verdeBioBolsa);

        Paragraph headerRegimen = new Paragraph("Régimen Común")
                .setFont(comic)
                .setFontSize(12)
                .setBold()
                .setFontColor(verdeBioBolsa);

        Paragraph headerIdentificador = new Paragraph("NIT: 900.390.537-1")
                .setFont(comic)
                .setFontSize(12)
                .setFontColor(verdeBioBolsa);

        Paragraph footerTelefonosAsesor = new Paragraph("Tels: (57) (1) 7137516 EXT 1142 – 7138731 - 2033205 Cel: (57) 300 275 45 51")
                .setFontSize(10)
                .setFontColor(verdeBioBolsa);

        Paragraph footerWebEmail = new Paragraph("Web: www.biobolsa.com.co   E-mail: [e-mail]")
                .setFontSize(10)
                .setFontColor(verdeBioBolsa);

        Paragraph footerDireccion = new Paragraph("Fábrica CRA 57 NO 45 A – 52 SUR LA SEVILLANA")
                .setFontSize(10)
                .setFontColor(verdeBioBolsa);

        Paragraph footerCiudad = new Paragraph("Bogotá D.C, Colombia")
                .setFontSize(10)
                .setFontColor(verdeBioBolsa);

        for (int i = 1; i <= document.getPdfDocument().getNumberOfPages(); i++) {

            System.out.println("PAGINA DEL PDF" + i);
            try {
                Rectangle pageSize = document.getPdfDocument().getPage(i).getPageSize();
                //Rectangle pageSize = document.getPdfDocument().getPage(i).getMediaBox();
                System.out.println("RECTANGLE....." + pageSize);
            } catch (Exception e) {
                // TODO: handle exception
                System.out.println("EXCEPCION RECTANGULO..." + e);
            }
        }
      }
   }
}

Answer

In short

The problem is due to your code accessing pages which iText already has flushed out of memory to the target file. You can instruct iText not to flush pages early by using the three-parameter Document constructor and setting the immediateFlush parameter to false, i.e. by replacing

try (Document document = new Document(pdf)) {

by

try (Document document = new Document(pdf, pdf.getDefaultPageSize(), false)) {

Some explanations

iText is designed to be usable in contexts in which huge PDFs (or many PDFs concurrently) can be generated without requiring a correspondingly huge amount of memory. It lowers its memory footprint by writing finished parts of the PDF to its output target and removing them from memory. In particular when creating multi-page documents, usually only the current and the previous page remain in memory while pages before that are flushed and have the contents of the remaining page object set to null.

So when you eventually iterate over all the pages of your PDF, all but the most recent ones indeed don’t have their MediaBox entries anymore, so you get a NullPointerException when trying to access the page size.

For use cases like yours in which early flushing is not appropriate, iText offers the flag used above to keep it from flushing pages early.

As an aside…

… if you wonder why your question has not been answered earlier: You posted a gigantic piece of code which one couldn’t even execute to reproduce the issue as you did not provide a JSON string for the data parameter. To be able to reproduce the issue, therefore, I had to cut down your code to the essential core that reproduces the issue:

public void createPdf(String dest) throws IOException {

    PdfDocument pdf = new PdfDocument(new PdfWriter(dest));
    try (Document document = new Document(pdf)) {

        document.setMargins(120, 36, 120, 36);

        document.add(new Paragraph("some content"));
        document.add(new AreaBreak(AreaBreakType.NEXT_PAGE));
        document.add(new Paragraph("some more content"));
        document.add(new AreaBreak(AreaBreakType.NEXT_PAGE));
        document.add(new Paragraph("still more content"));

        for (int i = 1; i <= document.getPdfDocument().getNumberOfPages(); i++) {

            System.out.println("PAGINA DEL PDF" + i);
            try {
                Rectangle pageSize = document.getPdfDocument().getPage(i).getPageSize();
                // Rectangle pageSize = document.getPdfDocument().getPage(i).getMediaBox();
                System.out.println("RECTANGLE....." + pageSize);
            } catch (Exception e) {
                // TODO: handle exception
                System.out.println("EXCEPCION RECTANGULO..." + e);
            }
        }
    }
}

If you had done so yourself, you would have had your question answered much earlier.