使用Spring RestTemplate提交带参数数据报错：Unexpected end of file from server

可能的原因及解决方案 #

1. 手动拼接JSON易导致格式错误 #

你当前手动拼接JSON字符串，一旦display.getBrightness()或display.getVolumelevel()是字符串类型（比如含特殊字符、空格），或者拼接时遗漏引号、括号，就会生成无效JSON。服务器解析失败后会提前关闭连接，触发"Unexpected end of file"错误。

修复方式：用对象/Map自动序列化JSON

• 方式一：创建DTO类

// 定义亮度请求DTO
class BrightnessRequest {
    private int brightness;
    
    public BrightnessRequest(int brightness) {
        this.brightness = brightness;
    }
    
    // 生成getter方法
    public int getBrightness() {
        return brightness;
    }
}

// 定义音量请求DTO
class VolumeRequest {
    private int musicvolume;
    
    public VolumeRequest(int musicvolume) {
        this.musicvolume = musicvolume;
    }
    
    // 生成getter方法
    public int getMusicvolume() {
        return musicvolume;
    }
}

// 使用示例
RestTemplate restTemplate = new RestTemplate();
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_JSON);

String endPointURL = "http://"+ display.getIpaddress()+"/api/brightness";
HttpEntity<BrightnessRequest> request = new HttpEntity<>(new BrightnessRequest(display.getBrightness()), httpHeaders);
// 服务器无响应体时，用Void.class作为响应类型
restTemplate.put(endPointURL, request, Void.class);

String endPointURL1 = "http://"+ display.getIpaddress()+"/api/volume";
HttpEntity<VolumeRequest> request1 = new HttpEntity<>(new VolumeRequest(display.getVolumelevel()), httpHeaders);
restTemplate.put(endPointURL1, request1, Void.class);

• 方式二：用HashMap快速构建请求体

RestTemplate restTemplate = new RestTemplate();
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_JSON);

String endPointURL = "http://"+ display.getIpaddress()+"/api/brightness";
Map<String, Object> brightnessMap = new HashMap<>();
brightnessMap.put("brightness", display.getBrightness());
HttpEntity<Map<String, Object>> request = new HttpEntity<>(brightnessMap, httpHeaders);
restTemplate.put(endPointURL, request, Void.class);

String endPointURL1 = "http://"+ display.getIpaddress()+"/api/volume";
Map<String, Object> volumeMap = new HashMap<>();
volumeMap.put("musicvolume", display.getVolumelevel());
HttpEntity<Map<String, Object>> request1 = new HttpEntity<>(volumeMap, httpHeaders);
restTemplate.put(endPointURL1, request1, Void.class);

2. RestTemplate PUT方法响应类型不匹配 #

如果服务器处理PUT请求后没有返回任何响应体，你指定String.class作为响应类型，RestTemplate会尝试读取不存在的响应内容，从而抛出EOF错误。

修复方式：改用Void.class作为响应类型
如上述代码所示，将restTemplate.put的第三个参数改为Void.class，明确告诉RestTemplate不需要解析响应体。

3. 排查网络和服务器问题 #

如果上述修复后仍报错，建议：

• 打印完整请求URL，确认IP地址和接口路径正确
• 用Postman/curl直接调用接口，验证服务器是否正常响应
• 给RestTemplate添加日志拦截器，打印请求头、请求体和响应详情，方便定位问题

// 添加日志拦截器示例
RestTemplate restTemplate = new RestTemplate();
ClientHttpRequestInterceptor interceptor = (request, body, execution) -> {
    System.out.println("Request URL: " + request.getURI());
    System.out.println("Request Body: " + new String(body, StandardCharsets.UTF_8));
    ClientHttpResponse response = execution.execute(request, body);
    System.out.println("Response Status: " + response.getStatusCode());
    return response;
};
restTemplate.getInterceptors().add(interceptor);

内容的提问来源于stack exchange，提问作者Anuja