★itext-爲pdf文件添加頁眉頁腳 | 3步完成 |

　　因爲上一篇自定義生成pdf的功能需求又增長了，須要加上頁碼。因此本博客誕生了~

　　1. 經過繼承PdfPageEventHelper類，實現須要實現的方法

　　

import com.lowagie.text.Document;
import com.lowagie.text.Element;
import com.lowagie.text.Phrase;
import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.ColumnText;
import com.lowagie.text.pdf.PdfPageEventHelper;
import com.lowagie.text.pdf.PdfWriter;

public class PdfBuilder extends PdfPageEventHelper {

　　// 噹噹前頁面開始加載時，觸發(頁眉)
    @Override
    public void onStartPage(PdfWriter writer, Document document) {
        // TODO Auto-generated method stub
        super.onStartPage(writer, document);
    }

　　// 噹噹前頁面初始化完成，切入document以前觸發(頁腳)
    @Override
    public void onEndPage(PdfWriter writer, Document document) {

        Rectangle rect = new Rectangle(0, 38, 50, 50);
        // ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER,
        // new Phrase(String.format("      ", writer.getPageNumber())), (rect.getLeft() + rect.getRight()) / 2,
        // rect.getBottom() - 18, 0);
        ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_BOTTOM,
                new Phrase(String.format("- %d -", writer.getPageNumber())), (rect.getLeft() + rect.getRight()) / 2,
                rect.getBottom() - 18, 0);
    }
}

tip： writer.getPageNumber();可以獲取到當前頁面的頁碼

2. 重寫一下ITextRenderer類

import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Shape;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.List;
import java.util.regex.Pattern;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xhtmlrenderer.css.style.CalculatedStyle;
import org.xhtmlrenderer.extend.NamespaceHandler;
import org.xhtmlrenderer.extend.UserInterface;
import org.xhtmlrenderer.layout.BoxBuilder;
import org.xhtmlrenderer.layout.Layer;
import org.xhtmlrenderer.layout.LayoutContext;
import org.xhtmlrenderer.layout.SharedContext;
import org.xhtmlrenderer.pdf.ITextFontContext;
import org.xhtmlrenderer.pdf.ITextFontResolver;
import org.xhtmlrenderer.pdf.ITextOutputDevice;
import org.xhtmlrenderer.pdf.ITextRenderer;
import org.xhtmlrenderer.pdf.ITextReplacedElementFactory;
import org.xhtmlrenderer.pdf.ITextTextRenderer;
import org.xhtmlrenderer.pdf.ITextUserAgent;
import org.xhtmlrenderer.pdf.PDFCreationListener;
import org.xhtmlrenderer.pdf.PDFEncryption;
import org.xhtmlrenderer.render.BlockBox;
import org.xhtmlrenderer.render.PageBox;
import org.xhtmlrenderer.render.RenderingContext;
import org.xhtmlrenderer.render.ViewportBox;
import org.xhtmlrenderer.resource.XMLResource;
import org.xhtmlrenderer.simple.extend.XhtmlNamespaceHandler;
import org.xhtmlrenderer.util.Configuration;
import org.xml.sax.InputSource;

import com.lowagie.text.DocumentException;
import com.lowagie.text.pdf.PdfPageEvent;
import com.lowagie.text.pdf.PdfWriter;

public class ITextRenderer2 {

    private ITextRenderer iTextRenderer = null;

    // These two defaults combine to produce an effective resolution of 96 px to the inch
    private static final float DEFAULT_DOTS_PER_POINT = 20f * 4f / 3f;
    private static final int DEFAULT_DOTS_PER_PIXEL = 20;

    private SharedContext _sharedContext;
    private ITextOutputDevice _outputDevice;

    private Document _doc;
    private BlockBox _root;

    private float _dotsPerPoint;

    private com.lowagie.text.Document _pdfDoc;
    private PdfWriter _writer;

    private PDFEncryption _pdfEncryption;

    // note: not hard-coding a default version in the _pdfVersion field as this may change between iText releases
    // check for null before calling writer.setPdfVersion()
    // use one of the values in PDFWriter.VERSION...
    private Character _pdfVersion;

    private char[] validPdfVersions = new char[] { PdfWriter.VERSION_1_2, PdfWriter.VERSION_1_3, PdfWriter.VERSION_1_4,
            PdfWriter.VERSION_1_5, PdfWriter.VERSION_1_6, PdfWriter.VERSION_1_7 };

    private PDFCreationListener _listener;

    private PdfPageEvent pdfPageEvent;

    public ITextRenderer2(ITextRenderer iTextRenderer) {
        this(DEFAULT_DOTS_PER_POINT, DEFAULT_DOTS_PER_PIXEL);
        this.iTextRenderer = iTextRenderer;
    }

    public ITextRenderer2() {
        this(DEFAULT_DOTS_PER_POINT, DEFAULT_DOTS_PER_PIXEL);
    }

    public ITextRenderer2(float dotsPerPoint, int dotsPerPixel) {
        _dotsPerPoint = dotsPerPoint;

        _outputDevice = new ITextOutputDevice(_dotsPerPoint);

        ITextUserAgent userAgent = new ITextUserAgent(_outputDevice);
        _sharedContext = new SharedContext(userAgent);
        userAgent.setSharedContext(_sharedContext);
        _outputDevice.setSharedContext(_sharedContext);

        ITextFontResolver fontResolver = new ITextFontResolver(_sharedContext);
        _sharedContext.setFontResolver(fontResolver);

        ITextReplacedElementFactory replacedElementFactory = new ITextReplacedElementFactory(_outputDevice);
        _sharedContext.setReplacedElementFactory(replacedElementFactory);

        _sharedContext.setTextRenderer(new ITextTextRenderer());
        _sharedContext.setDPI(72 * _dotsPerPoint);
        _sharedContext.setDotsPerPixel(dotsPerPixel);
        _sharedContext.setPrint(true);
        _sharedContext.setInteractive(false);
    }

    public PdfPageEvent getPdfPageEvent() {
        return pdfPageEvent;
    }

    public void setPdfPageEvent(PdfPageEvent pdfPageEvent) {
        this.pdfPageEvent = pdfPageEvent;
    }

    public ITextFontResolver getFontResolver() {
        return (ITextFontResolver) _sharedContext.getFontResolver();
    }

    private Document loadDocument(final String uri) {
        return _sharedContext.getUac().getXMLResource(uri).getDocument();
    }

    public void setDocument(String uri) {
        setDocument(loadDocument(uri), uri);
    }

    public void setDocument(Document doc, String url) {
        setDocument(doc, url, new XhtmlNamespaceHandler());
    }

    public void setDocument(File file) throws IOException {

        File parent = file.getAbsoluteFile().getParentFile();
        setDocument(loadDocument(file.toURI().toURL().toExternalForm()), (parent == null ? "" : parent.toURI().toURL()
                .toExternalForm()));
    }

    public void setDocumentFromString(String content) {
        InputSource is = new InputSource(new BufferedReader(new StringReader(content)));
        Document dom = XMLResource.load(is).getDocument();

        setDocument(dom, null);
    }

    public void setDocument(Document doc, String url, NamespaceHandler nsh) {
        _doc = doc;

        getFontResolver().flushFontFaceFonts();

        _sharedContext.reset();
        if (Configuration.isTrue("xr.cache.stylesheets", true)) {
            _sharedContext.getCss().flushStyleSheets();
        } else {
            _sharedContext.getCss().flushAllStyleSheets();
        }
        _sharedContext.setBaseURL(url);
        _sharedContext.setNamespaceHandler(nsh);
        _sharedContext.getCss().setDocumentContext(_sharedContext, _sharedContext.getNamespaceHandler(), doc,
                new NullUserInterface());
        getFontResolver().importFontFaces(_sharedContext.getCss().getFontFaceRules());
    }

    public PDFEncryption getPDFEncryption() {
        return _pdfEncryption;
    }

    public void setPDFEncryption(PDFEncryption pdfEncryption) {
        _pdfEncryption = pdfEncryption;
    }

    public void setPDFVersion(char _v) {
        for (int i = 0; i < validPdfVersions.length; i++) {
            if (_v == validPdfVersions[i]) {
                _pdfVersion = new Character(_v);
                return;
            }
        }
        throw new IllegalArgumentException("Invalid PDF version character; use "
                + "valid constants from PdfWriter (e.g. PdfWriter.VERSION_1_2)");
    }

    public char getPDFVersion() {
        return _pdfVersion == null ? '0' : _pdfVersion.charValue();
    }

    public void layout() {
        LayoutContext c = newLayoutContext();
        BlockBox root = BoxBuilder.createRootBox(c, _doc);
        root.setContainingBlock(new ViewportBox(getInitialExtents(c)));
        root.layout(c);
        Dimension dim = root.getLayer().getPaintingDimension(c);
        root.getLayer().trimEmptyPages(c, dim.height);
        root.getLayer().layoutPages(c);
        _root = root;
    }

    private Rectangle getInitialExtents(LayoutContext c) {
        PageBox first = Layer.createPageBox(c, "first");

        return new Rectangle(0, 0, first.getContentWidth(c), first.getContentHeight(c));
    }

    private RenderingContext newRenderingContext() {
        RenderingContext result = _sharedContext.newRenderingContextInstance();
        result.setFontContext(new ITextFontContext());

        result.setOutputDevice(_outputDevice);

        _sharedContext.getTextRenderer().setup(result.getFontContext());

        result.setRootLayer(_root.getLayer());

        return result;
    }

    private LayoutContext newLayoutContext() {
        LayoutContext result = _sharedContext.newLayoutContextInstance();
        result.setFontContext(new ITextFontContext());

        _sharedContext.getTextRenderer().setup(result.getFontContext());

        return result;
    }

    public void createPDF(OutputStream os) throws DocumentException {
        createPDF(os, true, 0);
    }

    public void writeNextDocument() throws DocumentException {
        writeNextDocument(0);
    }

    public void writeNextDocument(int initialPageNo) throws DocumentException {
        List pages = _root.getLayer().getPages();

        RenderingContext c = newRenderingContext();
        c.setInitialPageNo(initialPageNo);
        PageBox firstPage = (PageBox) pages.get(0);
        com.lowagie.text.Rectangle firstPageSize = new com.lowagie.text.Rectangle(0, 0, firstPage.getWidth(c)
                / _dotsPerPoint, firstPage.getHeight(c) / _dotsPerPoint);

        _outputDevice.setStartPageNo(_writer.getPageNumber());

        _pdfDoc.setPageSize(firstPageSize);
        _pdfDoc.newPage();

        writePDF(pages, c, firstPageSize, _pdfDoc, _writer);
    }

    public void finishPDF() {
        if (_pdfDoc != null) {
            fireOnClose();
            _pdfDoc.close();
        }
    }

    public void createPDF(OutputStream os, boolean finish) throws DocumentException {
        createPDF(os, finish, 0);
    }

    /**
     * <B>NOTE:</B> Caller is responsible for cleaning up the OutputStream if something goes wrong.
     */
    public void createPDF(OutputStream os, boolean finish, int initialPageNo) throws DocumentException {
        List pages = _root.getLayer().getPages();

        RenderingContext c = newRenderingContext();
        c.setInitialPageNo(initialPageNo);
        PageBox firstPage = (PageBox) pages.get(0);
        com.lowagie.text.Rectangle firstPageSize = new com.lowagie.text.Rectangle(0, 0, firstPage.getWidth(c)
                / _dotsPerPoint, firstPage.getHeight(c) / _dotsPerPoint);

        com.lowagie.text.Document doc = new com.lowagie.text.Document(firstPageSize, 0, 0, 0, 0);
        PdfWriter writer = PdfWriter.getInstance(doc, os);
        if (_pdfVersion != null) {
            writer.setPdfVersion(_pdfVersion.charValue());
        }
        if (_pdfEncryption != null) {
            writer.setEncryption(_pdfEncryption.getUserPassword(), _pdfEncryption.getOwnerPassword(),
                    _pdfEncryption.getAllowedPrivileges(), _pdfEncryption.getEncryptionType());
        }
        _pdfDoc = doc;
        _writer = writer;

        firePreOpen();

        if (pdfPageEvent != null) {
            writer.setPageEvent(pdfPageEvent);
        }

        doc.open();

        writePDF(pages, c, firstPageSize, doc, writer);

        if (finish) {
            fireOnClose();
            doc.close();
        }
    }

    private void firePreOpen() {
        if (_listener != null) {
            _listener.preOpen(iTextRenderer);
        }
    }

    private void fireOnClose() {
        if (_listener != null) {
            _listener.onClose(iTextRenderer);
        }
    }

    private void writePDF(List pages, RenderingContext c, com.lowagie.text.Rectangle firstPageSize,
            com.lowagie.text.Document doc, PdfWriter writer) throws DocumentException {
        _outputDevice.setRoot(_root);

        _outputDevice.start(_doc);
        _outputDevice.setWriter(writer);
        _outputDevice.initializePage(writer.getDirectContent(), firstPageSize.getHeight());

        _root.getLayer().assignPagePaintingPositions(c, Layer.PAGED_MODE_PRINT);

        int pageCount = _root.getLayer().getPages().size();
        c.setPageCount(pageCount);
        for (int i = 0; i < pageCount; i++) {
            PageBox currentPage = (PageBox) pages.get(i);
            c.setPage(i, currentPage);
            paintPage(c, writer, currentPage);
            _outputDevice.finishPage();
            if (i != pageCount - 1) {
                PageBox nextPage = (PageBox) pages.get(i + 1);
                com.lowagie.text.Rectangle nextPageSize = new com.lowagie.text.Rectangle(0, 0, nextPage.getWidth(c)
                        / _dotsPerPoint, nextPage.getHeight(c) / _dotsPerPoint);
                doc.setPageSize(nextPageSize);
                doc.newPage();
                _outputDevice.initializePage(writer.getDirectContent(), nextPageSize.getHeight());
            }
        }

        _outputDevice.finish(c, _root);
    }

    private void paintPage(RenderingContext c, PdfWriter writer, PageBox page) {
        provideMetadataToPage(writer, page);

        page.paintBackground(c, 0, Layer.PAGED_MODE_PRINT);
        page.paintMarginAreas(c, 0, Layer.PAGED_MODE_PRINT);
        page.paintBorder(c, 0, Layer.PAGED_MODE_PRINT);

        Shape working = _outputDevice.getClip();

        Rectangle content = page.getPrintClippingBounds(c);
        _outputDevice.clip(content);

        int top = -page.getPaintingTop() + page.getMarginBorderPadding(c, CalculatedStyle.TOP);

        int left = page.getMarginBorderPadding(c, CalculatedStyle.LEFT);

        _outputDevice.translate(left, top);
        _root.getLayer().paint(c);
        _outputDevice.translate(-left, -top);

        _outputDevice.setClip(working);
    }

    private void provideMetadataToPage(PdfWriter writer, PageBox page) {
        byte[] metadata = null;
        if (page.getMetadata() != null) {
            try {
                String metadataBody = stringfyMetadata(page.getMetadata());
                if (metadataBody != null) {
                    metadata = createXPacket(stringfyMetadata(page.getMetadata())).getBytes("UTF-8");
                }
            } catch (UnsupportedEncodingException e) {
                // Can't happen
                throw new RuntimeException(e);
            }
        }

        writer.setPageXmpMetadata(metadata);
    }

    private String stringfyMetadata(Element element) {
        Element target = getFirstChildElement(element);
        if (target == null) {
            return null;
        }

        try {
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer transformer = factory.newTransformer();
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            StringWriter output = new StringWriter();
            transformer.transform(new DOMSource(target), new StreamResult(output));

            return output.toString();
        } catch (TransformerConfigurationException e) {
            // Things must be in pretty bad shape to get here so
            // rethrow as runtime exception
            throw new RuntimeException(e);
        } catch (TransformerException e) {
            throw new RuntimeException(e);
        }
    }

    private static Element getFirstChildElement(Element element) {
        Node n = element.getFirstChild();
        while (n != null) {
            if (n.getNodeType() == Node.ELEMENT_NODE) {
                return (Element) n;
            }
            n = n.getNextSibling();
        }
        return null;
    }

    private String createXPacket(String metadata) {
        StringBuffer result = new StringBuffer(metadata.length() + 50);
        result.append("<?xpacket begin='\uFEFF' id='W5M0MpCehiHzreSzNTczkc9d'?>\n");
        result.append(metadata);
        result.append("\n<?xpacket end='r'?>");

        return result.toString();
    }

    public ITextOutputDevice getOutputDevice() {
        return _outputDevice;
    }

    public SharedContext getSharedContext() {
        return _sharedContext;
    }

    public void exportText(Writer writer) throws IOException {
        RenderingContext c = newRenderingContext();
        c.setPageCount(_root.getLayer().getPages().size());
        _root.exportText(c, writer);
    }

    public BlockBox getRootBox() {
        return _root;
    }

    public float getDotsPerPoint() {
        return _dotsPerPoint;
    }

    public List findPagePositionsByID(Pattern pattern) {
        return _outputDevice.findPagePositionsByID(newLayoutContext(), pattern);
    }

    private static final class NullUserInterface implements UserInterface {
        public boolean isHover(Element e) {
            return false;
        }

        public boolean isActive(Element e) {
            return false;
        }

        public boolean isFocus(Element e) {
            return false;
        }
    }

    public PDFCreationListener getListener() {
        return _listener;
    }

    public void setListener(PDFCreationListener listener) {
        _listener = listener;
    }

    public PdfWriter getWriter() {
        return _writer;
    }
}

　　tip： 因爲繼承沒法獲取部分私有變量和方法，動態代理方式在此處不可用，於是選擇重寫該類，在重寫的類ITextRenderer2中維護了一個ITextRenderer對象，使其內部功能正常執行，咱們只須要爲ITextRenderer2額外維護一個PdfPageEvent對象，而後在createPDF　　方法中，非空賦值一下便可。注意爲PdfWriter設置PdfPageEvent實現類的操做必須在document.open()以前。

　　3. 拿到html文件，進行html轉pdf操做

　　　　　　　　　 String url = htmlFile.toURI().toURL().toString();
              
                ITextRenderer2 renderer = new ITextRenderer2(new ITextRenderer());
                renderer.setDocument(url);
                ITextFontResolver fontResolver = renderer.getFontResolver();
                fontResolver.addFont(pdfFont + File.separator + "SimSun.ttc", BaseFont.IDENTITY_H,
                        BaseFont.NOT_EMBEDDED);
                fontResolver
                        .addFont(pdfFont + File.separator + "Arial.ttf", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
                renderer.setPdfPageEvent(new PDFBuilder());
                renderer.layout();
                renderer.createPDF(fos);

　　總結: 用了個人上一篇pdf生成技術(java原裝代碼完成pdf在線預覽和pdf打印及下載)的童鞋，若是也碰到了這樣的需求，能夠參考一下本篇博客哦
　　代碼改動量少，總共增長了2個類，改動了一行代碼，便可完成pdf的頁眉頁腳的添加。

　　經過這個例子，其實對於咱們是有啓示的，一種技術他能長久的在it行業中被你們一直所使用，不單單由於它自身功能的強大，也由於它在不少地方提供了可供程序員操做的接口或者類，使得這門技術可以不斷適合程序員的需求，而一個技術即使功能再強大，在全面，不開放可供他人操做的入口，依舊會被淘汰，由於其自身不可能適合全部程序員，只有程序員知道本身所須要的，那麼對於程序員來講，根據公司需求作出功能，咱們則要謹記爲功能安全的開放部分入口，這樣以便在後期需求更新時，可以儘量的不改變源代碼的基礎上進行需求更新，同時，也方便了其餘同事進行功能加強等一系列操做。以上純屬本人我的看法，如有不足，還望賜教~