场景描述：请求 Content Type 为 application/x-www-form-urlencoded，即参数以键值对形式传递，其中有简单类型，如：数字，字符串，也有 JSON 类型，需要绑定到 Spring 的模型中，完成校验。
参数格式参考如下，为了便于显示，进行了换行:
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| lesson_date=2022-08-08
&lesson_period_id=1
&subject_id=1
&grade_id=1
&class_id=1
&teacher_id=1
&student_list=[{"x":0,"y":0,"speak_num":0,"distract_num":0,"is_special":0}]
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如何支持下划线传参映射到 Model 模型? 装饰器模式 Request
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| public class MultiParamCaseRequest extends HttpServletRequestWrapper {
private final Map<String, String[]> additionalParams;
public MultiParamCaseRequest(HttpServletRequest request, Map<String, String[]> additionalParams) {
super(request);
this.additionalParams = additionalParams;
}
@Override
public Enumeration<String> getParameterNames() {
final HashSet<String> parameterNames = new HashSet<>();
parameterNames.addAll(getRequest().getParameterMap().keySet());
parameterNames.addAll(additionalParams.keySet());
return Collections.enumeration(parameterNames);
}
@Override
public String getParameter(String name) {
final String parameter = super.getParameter(name);
if (parameter != null) {
return parameter;
}
final String[] parameterValues = additionalParams.get(name);
if (parameterValues != null) {
if (parameterValues.length == 0) {
return "";
}
return parameterValues[0];
}
return null;
}
@Override
public String[] getParameterValues(String name) {
final String[] parameterValues = super.getParameterValues(name);
if (parameterValues != null) {
return parameterValues;
}
return additionalParams.get(name);
}
}
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| @Component
public class ParamNameExtensionFilter extends HttpFilter {
private final Pattern underLinePattern = Pattern.compile("_(\\w)");
@Override
protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
Map<String, String[]> additionalParams = new HashMap<>();
final Enumeration<String> parameterNames = request.getParameterNames();
final Map<String, String[]> parameterMap = request.getParameterMap();
while (parameterNames.hasMoreElements()) {
final String parameterName = parameterNames.nextElement();
final String camelCaseParameterName = this.underLineToCamel(parameterName);
if (parameterName.equals(camelCaseParameterName)) {
continue;
}
final String[] values = parameterMap.get(parameterName);
additionalParams.put(camelCaseParameterName, values);
}
final MultiParamCaseRequest multiParamCaseRequest = new MultiParamCaseRequest(request, additionalParams);
chain.doFilter(multiParamCaseRequest, response);
}
private String underLineToCamel(final String value) {
final StringBuffer sb = new StringBuffer();
Matcher m = this.underLinePattern.matcher(value);
while (m.find()) {
m.appendReplacement(sb, m.group(1).toUpperCase());
}
m.appendTail(sb);
return sb.toString();
}
}
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如果 Model 对象包含 Collection，需要定制 DataBinder:
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| @InitBinder
public void initBinder(WebDataBinder dataBinder) {
dataBinder.registerCustomEditor(List.class, "studentList", new PropertyEditorSupport() {
@Override
public void setAsText(String text) throws IllegalArgumentException {
if (StringUtils.isEmpty(text)) {
setValue(Collections.EMPTY_LIST);
} else {
final ObjectMapper objectMapper = new ObjectMapper();
try {
setValue(objectMapper.readValue(text, new TypeReference<List<EvaluationVO.Student>>() {
}));
} catch (JsonProcessingException e) {
throw new RuntimeException(e);
}
}
}
});
}
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