SXSSFWorkbook 表格内换行

起因

导出的excel需要在表格内换行，但搜索到的方法都实现不了我的需求，经同事搜查得知，这是POI的一个bug，已经在17年八月后被解决。

生成方式

pom依赖

		<dependency>
			<groupId>org.apache.poigroupId>
			<artifactId>poiartifactId>
			<version>4.0.0version>
		dependency>
		<dependency>
			<groupId>org.apache.poigroupId>
			<artifactId>poi-excelantartifactId>
			<version>4.0.0version>
		dependency>

生成excel换行代码

@Test
    public void test() throws IOException {
       
        Workbook wb = new SXSSFWorkbook();   //or new HSSFWorkbook();
        Sheet sheet = wb.createSheet();

        Row row = sheet.createRow(2);
        Cell cell = row.createCell(3);
        XSSFRichTextString rich = new XSSFRichTextString("测试\r" + "换行");
        cell.setCellValue(rich);

        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setWrapText(true);

        cell.setCellStyle(cellStyle);

        try (OutputStream fileOut = new FileOutputStream("ooxml-newlines.xlsx")) {
            wb.write(fileOut);
        }
    }

代码解析

SXSSFWorkbook是先将数据生成xml存储在本地，转化的时候会对表格内数据进行转义，具体代码见
org.apache.poi.xssf.streaming.SheetDataWriter#outputQuotedString()方法，内部代码为：

 String codepoint = (String)var2.next();
                byte var5 = -1;
                switch(codepoint.hashCode()) {
                case 9:
                    if (codepoint.equals("\t")) {
                        var5 = 6;
                    }
                    break;
                case 10:
                    if (codepoint.equals("\n")) {
                        var5 = 4;
                    }
                    break;
                case 13:
                    if (codepoint.equals("\r")) {
                        var5 = 5;
                    }
                    break;
                case 34:
                    if (codepoint.equals("\"")) {
                        var5 = 3;
                    }
                    break;
                case 38:
                    if (codepoint.equals("&")) {
                        var5 = 2;
                    }
                    break;
                case 60:
                    if (codepoint.equals("<")) {
                        var5 = 0;
                    }
                    break;
                case 62:
                    if (codepoint.equals(">")) {
                        var5 = 1;
                    }
                    break;
                case 160:
                    if (codepoint.equals(" ")) {
                        var5 = 7;
                    }
                }

                switch(var5) {
                case 0:
                    this._out.write("<");
                    break;
                case 1:
                    this._out.write(">");
                    break;
                case 2:
                    this._out.write("&");
                    break;
                case 3:
                    this._out.write(""");
                    break;
                case 4:
                    this._out.write("
");
                    break;
                case 5:
                    this._out.write("
");
                    break;
                case 6:
                    this._out.write("	");
                    break;
                case 7:
                    this._out.write(" ");
                    break;
                default:
                    if (codepoint.length() == 1) {
                        char c = codepoint.charAt(0);
                        if (replaceWithQuestionMark(c)) {
                            this._out.write(63);
                        } else {
                            this._out.write(c);
                        }
                    } else {
                        this._out.write(codepoint);
                    }
                }

由上可见，\r会被解析成 ，这个字符会被excel解析成换行，以此来达到换行的目的。而我之前使用的是3.9的版本，那个版本里会将\r和 \n都解析成 ,这个字符会被excel解析成空格，而不是换行。