export-compress.md

导出文件压缩

1 导出文件

• 1.1 设置返回的请求头

Response Header	Value	Desc
Content-type	application/json	资源的MIME类型
Content-Disposition	attachment;filename=xxx.json	展示形式

• 1.2 获取请求导出的资源并写入输出流

response.setCharacterEncoding("UTF-8");
response.setContentType("application/json");
response.addHeader("Content-Disposition", "attachment;filename=xxx.json");
    
String content = ...; // 此处导出字符串
try (ServletOutputStream outStr = response.getOutputStream();
    BufferedOutputStream buff = new BufferedOutputStream(outStr)) {
    buff.write(content.getBytes(StandardCharsets.UTF_8));
    buff.flush();
} catch (Exception e) {
    e.printStackTrace();
}

2 导出文件并压缩

2.1 使用压缩工具Apache Commons Compress

• 引入POM依赖

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-compress -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-compress</artifactId>
    <version>1.22</version>
</dependency>

• 加入Zip压缩

ZipArchiveOutputStream zipOutput = ...;
ZipArchiveEntry entry = new ZipArchiveEntry(name);
entry.setSize(size);
zipOutput.putArchiveEntry(entry);
zipOutput.write(contentOfEntry);
zipOutput.closeArchiveEntry();

• 多个文件加入Zip压缩

response.setCharacterEncoding("UTF-8");
response.addHeader("Content-Disposition", "attachment;filename=xxx.zip");
response.setContentType("application/zip");
    
List<content> texts = ...; // 此处导出字符串列表
try (ServletOutputStream outStr = response.getOutputStream();
    ZipArchiveOutputStream zipOutput = new ZipArchiveOutputStream(outStr)) {
    for (int i = 0; i < texts.size(); i++) {
        byte[] content = texts.get(i).getBytes(StandardCharsets.UTF_8)
        String entryName = "xxx_" + i + ".txt" 
        ZipArchiveEntry entry = new ZipArchiveEntry (entryName);
        entry.setSize(content.length);
        zipOutput.putArchiveEntry(entry);
        zipOutput.write(content);
        zipOutput.closeArchiveEntry();
    }
} catch (IOException e) {
     e.printStackTrace();
}

3 示例代码

• README