Java 如何将PNG图像从Jersey REST服务方法返回到浏览器
我有一个运行Jersey REST资源的web服务器,我想知道如何获取浏览器img标记的图像/png参考;提交表单或获得Ajax响应后。用于添加图形的图像处理代码正在运行,只需以某种方式返回它 代码:Java 如何将PNG图像从Jersey REST服务方法返回到浏览器,java,image,glassfish,jersey,javax.imageio,Java,Image,Glassfish,Jersey,Javax.imageio,我有一个运行Jersey REST资源的web服务器,我想知道如何获取浏览器img标记的图像/png参考;提交表单或获得Ajax响应后。用于添加图形的图像处理代码正在运行,只需以某种方式返回它 代码: 干杯我不认为在REST服务中返回图像数据是个好主意。它会占用应用服务器的内存和IO带宽。最好将该任务委托给适当的web服务器,该服务器针对此类传输进行了优化。您可以通过向映像资源发送重定向(作为带有映像URI的HTTP 302响应)来实现这一点。当然,这假设您的图像被安排为web内容 话虽如此,如
干杯我不认为在REST服务中返回图像数据是个好主意。它会占用应用服务器的内存和IO带宽。最好将该任务委托给适当的web服务器,该服务器针对此类传输进行了优化。您可以通过向映像资源发送重定向(作为带有映像URI的HTTP 302响应)来实现这一点。当然,这假设您的图像被安排为web内容 话虽如此,如果您决定确实需要从web服务传输图像数据,可以使用以下(伪)代码:
插件异常处理等。我为此构建了一个通用方法,具有以下功能:
- 返回“未修改”如果文件未在本地修改,则会向调用者发送Status.not_modified。使用
- 使用文件流对象而不是读取文件本身
import org.apache.commons.lang3.time.DateUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
private static final Logger logger = LoggerFactory.getLogger(Utils.class);
@GET
@Path("16x16")
@Produces("image/png")
public Response get16x16PNG(@HeaderParam("If-Modified-Since") String modified) {
File repositoryFile = new File("c:/temp/myfile.png");
return returnFile(repositoryFile, modified);
}
/**
*
* Sends the file if modified and "not modified" if not modified
* future work may put each file with a unique id in a separate folder in tomcat
* * use that static URL for each file
* * if file is modified, URL of file changes
* * -> client always fetches correct file
*
* method header for calling method public Response getXY(@HeaderParam("If-Modified-Since") String modified) {
*
* @param file to send
* @param modified - HeaderField "If-Modified-Since" - may be "null"
* @return Response to be sent to the client
*/
public static Response returnFile(File file, String modified) {
if (!file.exists()) {
return Response.status(Status.NOT_FOUND).build();
}
// do we really need to send the file or can send "not modified"?
if (modified != null) {
Date modifiedDate = null;
// we have to switch the locale to ENGLISH as parseDate parses in the default locale
Locale old = Locale.getDefault();
Locale.setDefault(Locale.ENGLISH);
try {
modifiedDate = DateUtils.parseDate(modified, org.apache.http.impl.cookie.DateUtils.DEFAULT_PATTERNS);
} catch (ParseException e) {
logger.error(e.getMessage(), e);
}
Locale.setDefault(old);
if (modifiedDate != null) {
// modifiedDate does not carry milliseconds, but fileDate does
// therefore we have to do a range-based comparison
// 1000 milliseconds = 1 second
if (file.lastModified()-modifiedDate.getTime() < DateUtils.MILLIS_PER_SECOND) {
return Response.status(Status.NOT_MODIFIED).build();
}
}
}
// we really need to send the file
try {
Date fileDate = new Date(file.lastModified());
return Response.ok(new FileInputStream(file)).lastModified(fileDate).build();
} catch (FileNotFoundException e) {
return Response.status(Status.NOT_FOUND).build();
}
}
/*** copied from org.apache.http.impl.cookie.DateUtils, Apache 2.0 License ***/
/**
* Date format pattern used to parse HTTP date headers in RFC 1123 format.
*/
public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
/**
* Date format pattern used to parse HTTP date headers in RFC 1036 format.
*/
public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
/**
* Date format pattern used to parse HTTP date headers in ANSI C
* <code>asctime()</code> format.
*/
public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
public static final String[] DEFAULT_PATTERNS = new String[] {
PATTERN_RFC1036,
PATTERN_RFC1123,
PATTERN_ASCTIME
};
请注意,区域设置切换似乎不是线程安全的。我认为,最好在全球范围内切换区域设置。我不确定副作用是什么…关于@Perception的回答,在使用字节数组时确实会消耗大量内存,但您也可以简单地写回outputstream
@Path("/picture")
public class ProfilePicture {
@GET
@Path("/thumbnail")
@Produces("image/png")
public StreamingOutput getThumbNail() {
return new StreamingOutput() {
@Override
public void write(OutputStream os) throws IOException, WebApplicationException {
//... read your stream and write into os
}
};
}
}
如果您有许多图像资源方法,那么创建MessageBodyWriter以输出BuffereImage是非常值得的:
@Produces({ "image/png", "image/jpg" })
@Provider
public class BufferedImageBodyWriter implements MessageBodyWriter<BufferedImage> {
@Override
public boolean isWriteable(Class<?> type, Type type1, Annotation[] antns, MediaType mt) {
return type == BufferedImage.class;
}
@Override
public long getSize(BufferedImage t, Class<?> type, Type type1, Annotation[] antns, MediaType mt) {
return -1; // not used in JAX-RS 2
}
@Override
public void writeTo(BufferedImage image, Class<?> type, Type type1, Annotation[] antns, MediaType mt, MultivaluedMap<String, Object> mm, OutputStream out) throws IOException, WebApplicationException {
ImageIO.write(image, mt.getSubtype(), out);
}
}
这种方法有几个优点:
- 它写入响应OutputSteam,而不是中间缓冲输出流
- 它支持png和jpg输出(取决于资源方法允许的媒体类型)
CacheControll cc=new CacheControl();抄送setMaxAge(编号);响应(..).cacheControl(cc.build()代码>。您可以使用Jersey的Request.evaluatePreconditions(…)删除许多上次修改的逻辑,因为它将处理解析和检查日期以及ETag(如果您支持的话)。
@Path("/picture")
public class ProfilePicture {
@GET
@Path("/thumbnail")
@Produces("image/png")
public StreamingOutput getThumbNail() {
return new StreamingOutput() {
@Override
public void write(OutputStream os) throws IOException, WebApplicationException {
//... read your stream and write into os
}
};
}
}
@Produces({ "image/png", "image/jpg" })
@Provider
public class BufferedImageBodyWriter implements MessageBodyWriter<BufferedImage> {
@Override
public boolean isWriteable(Class<?> type, Type type1, Annotation[] antns, MediaType mt) {
return type == BufferedImage.class;
}
@Override
public long getSize(BufferedImage t, Class<?> type, Type type1, Annotation[] antns, MediaType mt) {
return -1; // not used in JAX-RS 2
}
@Override
public void writeTo(BufferedImage image, Class<?> type, Type type1, Annotation[] antns, MediaType mt, MultivaluedMap<String, Object> mm, OutputStream out) throws IOException, WebApplicationException {
ImageIO.write(image, mt.getSubtype(), out);
}
}
@Path("/whatever")
@Produces({"image/png", "image/jpg"})
public Response getFullImage(...) {
BufferedImage image = ...;
return Response.ok(image).build();
}