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SpringBoot如何使用RequestBodyAdvice进行统一参数处理
什么是RequestBodyAdvice
RequestBodyAdvice是Spring框架提供的一个拦截HTTP请求体的接口。通过实现该接口的beforeBodyRead方法,我们可以在控制器方法执行前统一处理请求体,并返回修改后的请求体。
怎样实现RequestBodyAdvice
要实现RequestBodyAdvice,我们需要遵循以下步骤:
第一步:创建一个类,实现RequestBodyAdvice接口
@Component
public class MyRequestBodyAdvice implements RequestBodyAdvice {
@Override
public boolean supports(MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 需要拦截的参数类型,返回true
return true;
}
@Override
public HttpInputMessage beforeBodyRead(HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) throws IOException, HttpMessageNotReadableException {
// 处理请求体
return httpInputMessage;
}
@Override
public Object afterBodyRead(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
@Override
public Object handleEmptyBody(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
}
第二步:在MyRequestBodyAdvice类上使用@Component注解
这样SpringBoot就会自动扫描该类,并将其注册为Bean。
第三步:实现beforeBodyRead方法
在beforeBodyRead方法中,我们可以获取到原始的请求体,进行处理,并返回修改后的请求体。
假设我们的统一参数处理是把RequestBody中的所有参数都转换成大写字母。实现代码如下:
@Override
public HttpInputMessage beforeBodyRead(HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) throws IOException, HttpMessageNotReadableException {
InputStreamReader isr = new InputStreamReader(httpInputMessage.getBody(), StandardCharsets.UTF_8);
BufferedReader br = new BufferedReader(isr);
String body = br.lines().collect(Collectors.joining(System.lineSeparator()));
body = body.toUpperCase(); // 将RequestBody中的所有参数转换成大写字母
byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
return new ServletInputStreamHttpInputMessage(new ByteArrayInputStream(bytes), httpInputMessage.getHeaders()); // 返回修改后的请求体
}
第四步:在控制器方法中使用RequestBody参数
在控制器方法中,我们可以直接使用处理过后的请求体,例如:
@PostMapping("/test")
public String test(@RequestBody User user) {
// do something
}
经过上述步骤,RequestBody中所有参数都已经被转换成了大写字母。
示例说明
示例一:统一加上时间戳
现在我们要统一在RequestBody中的参数中加上当前时间戳。实现代码如下:
@Component
public class AddTimestampRequestBodyAdvice implements RequestBodyAdvice {
@Override
public boolean supports(MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 需要拦截的参数类型,返回true
return true;
}
@Override
public HttpInputMessage beforeBodyRead(HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) throws IOException, HttpMessageNotReadableException {
InputStreamReader isr = new InputStreamReader(httpInputMessage.getBody(), StandardCharsets.UTF_8);
BufferedReader br = new BufferedReader(isr);
String body = br.lines().collect(Collectors.joining(System.lineSeparator()));
ObjectMapper objectMapper = new ObjectMapper();
Map map = objectMapper.readValue(body, Map.class);
long timestamp = System.currentTimeMillis();
map.put("timestamp", timestamp);
byte[] bytes = objectMapper.writeValueAsBytes(map);
return new ServletInputStreamHttpInputMessage(new ByteArrayInputStream(bytes), httpInputMessage.getHeaders());
}
@Override
public Object afterBodyRead(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
@Override
public Object handleEmptyBody(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
}
上面的代码中,我们将RequestBody转换成了Map,然后在Map中加入了一个"timestamp"字段,值为当前时间戳。最后,我们将Map转换回RequestBody,并返回修改后的请求体。
使用示例:
@PostMapping("/user")
public void addUser(@RequestBody Map<String, Object> map) {
System.out.println(map);
// do something
}
示例二:统一加上机器名
同样是对RequestBody进行统一处理,不过这一次,我们要将机器名加入到每个参数的前面。实现代码如下:
@Component
public class AddHostnameRequestBodyAdvice implements RequestBodyAdvice {
private static String hostname = null;
@Override
public boolean supports(MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 需要拦截的参数类型,返回true
return true;
}
@Override
public HttpInputMessage beforeBodyRead(HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) throws IOException, HttpMessageNotReadableException {
InputStreamReader isr = new InputStreamReader(httpInputMessage.getBody(), StandardCharsets.UTF_8);
BufferedReader br = new BufferedReader(isr);
String body = br.lines().collect(Collectors.joining(System.lineSeparator()));
// 获取机器名
if (hostname == null) {
try {
InetAddress addr = InetAddress.getLocalHost();
hostname = addr.getHostName();
} catch (UnknownHostException e) {
hostname = "";
}
}
// 将机器名加入到RequestBody中每个参数的前面
ObjectMapper objectMapper = new ObjectMapper();
Map map = objectMapper.readValue(body, Map.class);
Map newMap = new HashMap();
for (Object key : map.keySet()) {
Object value = map.get(key);
newMap.put(hostname + "-" + key, value);
}
byte[] bytes = objectMapper.writeValueAsBytes(newMap);
return new ServletInputStreamHttpInputMessage(new ByteArrayInputStream(bytes), httpInputMessage.getHeaders());
}
@Override
public Object afterBodyRead(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
@Override
public Object handleEmptyBody(Object o, HttpInputMessage httpInputMessage, MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
// 不需要做任何处理
return o;
}
}
使用示例:
@PostMapping("/user")
public void addUser(@RequestBody Map<String, Object> map) {
System.out.println(map);
// do something
}
经过上述示例,我们可以看到RequestBody中的参数都被加上了机器名,以及时间戳。这样我们就可以在RequestBody中加入一些默认的信息,使得代码更加健壮,系统更加安全。
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