当使用Spring RestTemplate上传byte[]到SpringMVC rest端点时，错误请求

Question

我试图上传一个字节[]，其中包含一个图像到我的Spring rest服务(在Spring Boot中运行，btw)作为一个MultipartFile与我的客户端运行Spring RestTemplate，我得到httpclienterrorexcexception: 400 Bad Request。

我的端点:

@RequestMapping(value="/scale/{percent}", method= RequestMethod.POST)
public ResponseEntity scaleImage(@PathVariable("percent") float percent,
                                        @RequestParam("file") MultipartFile file) {
    try {
        if (!file.isEmpty()) {
            byte [] result = transformService.scaleImage(percent, file.getBytes());
            return getResponseEntityFromBytes(result);
        } else {
            return generateBadRequestError();
        }
    } catch (Exception e) {
        if (e instanceof InvalidOperationParameterException) {
            // TODO - populate message with bad parameters
            LOGGER.log(Level.FINE, "Invalid Parameters: ");
            return generateBadRequestError();
        } else {
            LOGGER.log(Level.SEVERE, "Exception caught: " + e.getMessage(), e);
            return generateServerError(e.getMessage());
        }
    }
}

My Spring RestTemplate client:

public void scaleImage(byte[] image, float percent) throws Exception {
    String url = "http://localhost:8080/scale/" + percent;
    this.testNumberThreads=10;
    this.testNumberThreads=10;
    MultiValueMap<String, Object> mvm = new LinkedMultiValueMap<>();
    mvm.add("file", image);
    TransformedResponse r = doPost(url, mvm);
}
private TransformedResponse doPost(String url, MultiValueMap<String, Object> mvm) {
    RestTemplate restTemplate = new RestTemplate();
    TransformedResponse xr = null;
    try {
        xr = restTemplate.postForObject(url, mvm, TransformedResponse.class);
    } catch (RestClientException e) {
        e.printStackTrace();
    }
    return xr;
}

…

public class TransformedResponse {
    byte[] image;
    public byte[] getImage() {
        return image;
    }
    public void setImage(byte[] image) {
        this.image = image;
    }
}

这是我在客户端看到的例外(还没有击中服务器):

org.springframework.web.client.HttpClientErrorException: 400 Bad Request
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:91)
    at org.springframework.web.client.RestTemplate.handleResponseError(RestTemplate.java:588)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:546)
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:502)
    at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:330)
    at com.me.image.xform.LoadTest.doPost(LoadTest.java:110)
    at com.me.image.xform.LoadTest.loadTestScalePercent(LoadTest.java:75)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:232)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:175)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)

为什么这个请求不能正确发布?

Answer 1

我找到我的问题了。我需要添加一个AbstractResource(在这种情况下是ByteArrayResource)到我的MultiValueMap，而不是原始字节数组。下面是修复它的代码:

public void scaleImage(byte[] image, float percent) throws Exception {
    String url = "http://localhost:8080/scale/" + percent;
    final byte[] rawBytes = image.clone();
    MultiValueMap<String, Object> mvm = new LinkedMultiValueMap<>();
    ByteArrayResource bar = new ByteArrayResource(rawBytes) {
        @Override
        public String getFilename() {
            return "Test-"+rawBytes.length + ".jpg";
        }
    };
    mvm.add("file", bar);
    TransformedResponse r = doPost(url, mvm);
}

Answer 2

首先，在使用Spring时，请确保在servlet上下文中定义了适当的MultiPartFile解析器:

<bean id="multipartResolver"
      class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="52428800"/>
    <property name="maxInMemorySize" value="52428800"/>
</bean>

如果你使用maven，这个解析器位于spring-web artifact中:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>${your.spring.version}</version>
</dependency>

然后，创建表单，确保使用正确的enctype:

<form method="post" action="upload.form" enctype="multipart/form-data">
    <input type="file" name="file"/>
    <input type="submit"/>
</form>

最后，处理控制器中的文件上传

@RequestMapping(value="/path", method= RequestMethod.POST)
public StringscaleImage(@RequestParam("file") MultipartFile file) {
    //....
}

请记住，异步文件上传只支持HTML5，与其他你需要使用一些变通方法(如flash或iframes)。

如果你仍然面临400错误，在你的日志服务中添加这个记录器(或类似的，取决于日志框架):

<appender name="console" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <param name="threshold" value="TRACE"/>
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{HH:mm:ss,SSS} %-5p [%c] %m%n"/>
    </layout>
</appender>
<logger name="org.springframework.web.method.HandlerMethod">
    <level value="TRACE"/>
</logger>
<root>
    <priority value="info"/>
    <appender-ref ref="console"/>
</root>

它应该输出在请求处理期间抛出的异常

Answer 3

不要尝试将MultipartFile作为请求参数传入，请尝试以下操作:

@RequestMapping(value="/scale/{percent}", method= RequestMethod.POST)
public ResponseEntity scaleImage(@PathVariable("percent") float percent,
        MultipartHttpServletRequest request) {
    Iterator<String> fileNames = request.getFileNames();
    MultipartFile uploadedFile = request.getFile(fileNames.next());
    String fileName = uploadedFile.getName();

这是唯一能让我的多部分文件被接受的方法。

如果你仍然从这个过程中得到一个空文件，它一定是与你如何POST数据有关。