在java中将JSON转换为PDF的最简单方法？

Question

我使用 Java Spring Boot 框架，我需要将我的 Json 转换为 PDF。问题是 PDF 中的所有文本都写在一行中，这意味着换行符不起作用。结果，我得到一个 PDF，其中第一行是空白或空文件。

 @GetMapping("/pdf/{Id}")
    @Secured({"ROLE_ADMIN", "ROLE_OPERATOR", "ROLE_GUEST"})
    public ResponseEntity<PDDocument> findOnePdfByIdJob(@PathVariable("Id") Long id) throws DocumentException, IOException {
        Job job = jobService.findById(id);

        if (job == null) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }

        ObjectMapper objectMapper = new ObjectMapper();
        String jsonInString = objectMapper.writeValueAsString(job);

        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        JsonParser jp = new JsonParser();
        JsonElement je = jp.parse(jsonInString);
        String prettyJsonString = gson.toJson(je);


        PDDocument document = new PDDocument();
        PDPage page = new PDPage();
        document.addPage(page);

        PDPageContentStream contentStream = new PDPageContentStream(document, page);

        contentStream.setFont(PDType1Font.COURIER, 12);
        contentStream.beginText();
        contentStream.showText(jsonInString);
        contentStream.endText();
        contentStream.close();

        document.save("pdfBoxHelloWorld.pdf");
        document.close();

        HttpHeaders headers = new HttpHeaders();
        headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
        headers.add("Pragma", "no-cache");
        headers.add("Expires", "0");

        return ResponseEntity.ok()
                .headers(headers)
                .contentType(MediaType.parseMediaType("application/octet-stream"))
                .body(document);
    }

因此，我得到了一个 PDF，其中所有内容都写在一行中。也就是无法读取文本....第一行变成了空行。

Answer 1

如果您已经使用Jackson 的ObjectMapper，则不需要使用Gson。只需启用SerializationFeature.INDENT_OUTPUT 功能，ObjectMapper 也会生成漂亮的JSON。此外，您需要在行上拆分JSON，并使用PDPageContentStream 中的newLine 方法逐行添加每一行。

简单的应用：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.type.MapType;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.font.PDType1Font;

import java.io.File;
import java.util.Map;

public class PdfApp {

    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        ObjectMapper mapper = new ObjectMapper();
        // enable pretty printing
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        // read map from file
        MapType mapType = mapper.getTypeFactory().constructMapType(Map.class, String.class, Object.class);
        Map<String, Object> map = mapper.readValue(jsonFile, mapType);

        // generate pretty JSON from map
        String json = mapper.writeValueAsString(map);
        // split by system new lines
        String[] strings = json.split(System.lineSeparator());

        PDDocument document = new PDDocument();
        PDPage page = new PDPage();
        document.addPage(page);

        PDPageContentStream contentStream = new PDPageContentStream(document, page);

        contentStream.setFont(PDType1Font.COURIER, 12);
        contentStream.beginText();
        contentStream.setLeading(14.5f);
        contentStream.newLineAtOffset(25, 725);
        for (String string : strings) {
            contentStream.showText(string);
            // add line manually
            contentStream.newLine();
        }
        contentStream.endText();
        contentStream.close();

        document.save("pdfBoxHelloWorld.pdf");
        document.close();
    }
}

生成PDF 文件，内容如下：

另见：

• PDFBox - Adding Multiple Lines
• PDFBOX : U+000A ('controlLF') is not available in this font Helvetica encoding: WinAnsiEncoding