How to customize parameter names when binding Spring MVC command objects?
In Spring 3.1, ServletRequestDataBinder provides a hook for additional bind values:
protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
}
The ExtendedServletRequestDataBinder subclass uses it to add URI template variables as binding values. You could extend it further to make it possible to add command-specific field aliases.
You can override RequestMappingHandlerAdapter.createDataBinderFactory(..) to provide a custom WebDataBinder instance. From a controller's perspective it could look like this:
@InitBinder
public void initBinder(MyWebDataBinder binder) {
binder.addFieldAlias("jobType", "jt");
// ...
}
This solution more concise but requires using RequestMappingHandlerAdapter, which Spring use when <mvc:annotation-driven /> enabled.
Hope it will help somebody.
The idea is to extend ServletRequestDataBinder like this:
/**
* ServletRequestDataBinder which supports fields renaming using {@link ParamName}
*
* @author jkee
*/
public class ParamNameDataBinder extends ExtendedServletRequestDataBinder {
private final Map<String, String> renameMapping;
public ParamNameDataBinder(Object target, String objectName, Map<String, String> renameMapping) {
super(target, objectName);
this.renameMapping = renameMapping;
}
@Override
protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
super.addBindValues(mpvs, request);
for (Map.Entry<String, String> entry : renameMapping.entrySet()) {
String from = entry.getKey();
String to = entry.getValue();
if (mpvs.contains(from)) {
mpvs.add(to, mpvs.getPropertyValue(from).getValue());
}
}
}
}
Appropriate processor:
/**
* Method processor supports {@link ParamName} parameters renaming
*
* @author jkee
*/
public class RenamingProcessor extends ServletModelAttributeMethodProcessor {
@Autowired
private RequestMappingHandlerAdapter requestMappingHandlerAdapter;
//Rename cache
private final Map<Class<?>, Map<String, String>> replaceMap = new ConcurrentHashMap<Class<?>, Map<String, String>>();
public RenamingProcessor(boolean annotationNotRequired) {
super(annotationNotRequired);
}
@Override
protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest nativeWebRequest) {
Object target = binder.getTarget();
Class<?> targetClass = target.getClass();
if (!replaceMap.containsKey(targetClass)) {
Map<String, String> mapping = analyzeClass(targetClass);
replaceMap.put(targetClass, mapping);
}
Map<String, String> mapping = replaceMap.get(targetClass);
ParamNameDataBinder paramNameDataBinder = new ParamNameDataBinder(target, binder.getObjectName(), mapping);
requestMappingHandlerAdapter.getWebBindingInitializer().initBinder(paramNameDataBinder, nativeWebRequest);
super.bindRequestParameters(paramNameDataBinder, nativeWebRequest);
}
private static Map<String, String> analyzeClass(Class<?> targetClass) {
Field[] fields = targetClass.getDeclaredFields();
Map<String, String> renameMap = new HashMap<String, String>();
for (Field field : fields) {
ParamName paramNameAnnotation = field.getAnnotation(ParamName.class);
if (paramNameAnnotation != null && !paramNameAnnotation.value().isEmpty()) {
renameMap.put(paramNameAnnotation.value(), field.getName());
}
}
if (renameMap.isEmpty()) return Collections.emptyMap();
return renameMap;
}
}
Annotation:
/**
* Overrides parameter name
* @author jkee
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ParamName {
/**
* The name of the request parameter to bind to.
*/
String value();
}
Spring config:
<mvc:annotation-driven>
<mvc:argument-resolvers>
<bean class="ru.yandex.metrika.util.params.RenamingProcessor">
<constructor-arg name="annotationNotRequired" value="true"/>
</bean>
</mvc:argument-resolvers>
</mvc:annotation-driven>
And finally, usage (like Bozho solution):
public class Job {
@ParamName("job-type")
private String jobType;
@ParamName("loc")
private String location;
}
Thanks the answer of @jkee .
Here is my solution.
First, a custom annotation:
@Inherited
@Documented
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ParamName {
/**
* The name of the request parameter to bind to.
*/
String value();
}
A customer DataBinder:
public class ParamNameDataBinder extends ExtendedServletRequestDataBinder {
private final Map<String, String> paramMappings;
public ParamNameDataBinder(Object target, String objectName, Map<String, String> paramMappings) {
super(target, objectName);
this.paramMappings = paramMappings;
}
@Override
protected void addBindValues(MutablePropertyValues mutablePropertyValues, ServletRequest request) {
super.addBindValues(mutablePropertyValues, request);
for (Map.Entry<String, String> entry : paramMappings.entrySet()) {
String paramName = entry.getKey();
String fieldName = entry.getValue();
if (mutablePropertyValues.contains(paramName)) {
mutablePropertyValues.add(fieldName, mutablePropertyValues.getPropertyValue(paramName).getValue());
}
}
}
}
A parameter resolver:
public class ParamNameProcessor extends ServletModelAttributeMethodProcessor {
@Autowired
private RequestMappingHandlerAdapter requestMappingHandlerAdapter;
private static final Map<Class<?>, Map<String, String>> PARAM_MAPPINGS_CACHE = new ConcurrentHashMap<>(256);
public ParamNameProcessor() {
super(false);
}
@Override
public boolean supportsParameter(MethodParameter parameter) {
return parameter.hasParameterAnnotation(RequestParam.class)
&& !BeanUtils.isSimpleProperty(parameter.getParameterType())
&& Arrays.stream(parameter.getParameterType().getDeclaredFields())
.anyMatch(field -> field.getAnnotation(ParamName.class) != null);
}
@Override
protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest nativeWebRequest) {
Object target = binder.getTarget();
Map<String, String> paramMappings = this.getParamMappings(target.getClass());
ParamNameDataBinder paramNameDataBinder = new ParamNameDataBinder(target, binder.getObjectName(), paramMappings);
requestMappingHandlerAdapter.getWebBindingInitializer().initBinder(paramNameDataBinder, nativeWebRequest);
super.bindRequestParameters(paramNameDataBinder, nativeWebRequest);
}
/**
* Get param mappings.
* Cache param mappings in memory.
*
* @param targetClass
* @return {@link Map<String, String>}
*/
private Map<String, String> getParamMappings(Class<?> targetClass) {
if (PARAM_MAPPINGS_CACHE.containsKey(targetClass)) {
return PARAM_MAPPINGS_CACHE.get(targetClass);
}
Field[] fields = targetClass.getDeclaredFields();
Map<String, String> paramMappings = new HashMap<>(32);
for (Field field : fields) {
ParamName paramName = field.getAnnotation(ParamName.class);
if (paramName != null && !paramName.value().isEmpty()) {
paramMappings.put(paramName.value(), field.getName());
}
}
PARAM_MAPPINGS_CACHE.put(targetClass, paramMappings);
return paramMappings;
}
}
Finally, a bean configuration for adding ParamNameProcessor into the first of argument resolvers:
@Configuration
public class WebConfig {
/**
* Processor for annotation {@link ParamName}.
*
* @return ParamNameProcessor
*/
@Bean
protected ParamNameProcessor paramNameProcessor() {
return new ParamNameProcessor();
}
/**
* Custom {@link BeanPostProcessor} for adding {@link ParamNameProcessor} into the first of
* {@link RequestMappingHandlerAdapter#argumentResolvers}.
*
* @return BeanPostProcessor
*/
@Bean
public BeanPostProcessor beanPostProcessor() {
return new BeanPostProcessor() {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof RequestMappingHandlerAdapter) {
RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter) bean;
List<HandlerMethodArgumentResolver> argumentResolvers = new ArrayList<>(adapter.getArgumentResolvers());
argumentResolvers.add(0, paramNameProcessor());
adapter.setArgumentResolvers(argumentResolvers);
}
return bean;
}
};
}
}
Param pojo:
@Data
public class Foo {
private Integer id;
@ParamName("first_name")
private String firstName;
@ParamName("last_name")
private String lastName;
@ParamName("created_at")
@DateTimeFormat(pattern = "yyyy-MM-dd")
private Date createdAt;
}
Controller method:
@GetMapping("/foos")
public ResponseEntity<List<Foo>> listFoos(@RequestParam Foo foo, @PageableDefault(sort = "id") Pageable pageable) {
List<Foo> foos = fooService.listFoos(foo, pageable);
return ResponseEntity.ok(foos);
}
That's all.
Here's what I got working:
First, a parameter resolver:
/**
* This resolver handles command objects annotated with @SupportsAnnotationParameterResolution
* that are passed as parameters to controller methods.
*
* It parses @CommandPerameter annotations on command objects to
* populate the Binder with the appropriate values (that is, the filed names
* corresponding to the GET parameters)
*
* In order to achieve this, small pieces of code are copied from spring-mvc
* classes (indicated in-place). The alternative to the copied lines would be to
* have a decorator around the Binder, but that would be more tedious, and still
* some methods would need to be copied.
*
* @author bozho
*
*/
public class AnnotationServletModelAttributeResolver extends ServletModelAttributeMethodProcessor {
/**
* A map caching annotation definitions of command objects (@CommandParameter-to-fieldname mappings)
*/
private ConcurrentMap<Class<?>, Map<String, String>> definitionsCache = Maps.newConcurrentMap();
public AnnotationServletModelAttributeResolver(boolean annotationNotRequired) {
super(annotationNotRequired);
}
@Override
public boolean supportsParameter(MethodParameter parameter) {
if (parameter.getParameterType().isAnnotationPresent(SupportsAnnotationParameterResolution.class)) {
return true;
}
return false;
}
@Override
protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest request) {
ServletRequest servletRequest = request.getNativeRequest(ServletRequest.class);
ServletRequestDataBinder servletBinder = (ServletRequestDataBinder) binder;
bind(servletRequest, servletBinder);
}
@SuppressWarnings("unchecked")
public void bind(ServletRequest request, ServletRequestDataBinder binder) {
Map<String, ?> propertyValues = parsePropertyValues(request, binder);
MutablePropertyValues mpvs = new MutablePropertyValues(propertyValues);
MultipartRequest multipartRequest = WebUtils.getNativeRequest(request, MultipartRequest.class);
if (multipartRequest != null) {
bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
}
// two lines copied from ExtendedServletRequestDataBinder
String attr = HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE;
mpvs.addPropertyValues((Map<String, String>) request.getAttribute(attr));
binder.bind(mpvs);
}
private Map<String, ?> parsePropertyValues(ServletRequest request, ServletRequestDataBinder binder) {
// similar to WebUtils.getParametersStartingWith(..) (prefixes not supported)
Map<String, Object> params = Maps.newTreeMap();
Assert.notNull(request, "Request must not be null");
Enumeration<?> paramNames = request.getParameterNames();
Map<String, String> parameterMappings = getParameterMappings(binder);
while (paramNames != null && paramNames.hasMoreElements()) {
String paramName = (String) paramNames.nextElement();
String[] values = request.getParameterValues(paramName);
String fieldName = parameterMappings.get(paramName);
// no annotation exists, use the default - the param name=field name
if (fieldName == null) {
fieldName = paramName;
}
if (values == null || values.length == 0) {
// Do nothing, no values found at all.
} else if (values.length > 1) {
params.put(fieldName, values);
} else {
params.put(fieldName, values[0]);
}
}
return params;
}
/**
* Gets a mapping between request parameter names and field names.
* If no annotation is specified, no entry is added
* @return
*/
private Map<String, String> getParameterMappings(ServletRequestDataBinder binder) {
Class<?> targetClass = binder.getTarget().getClass();
Map<String, String> map = definitionsCache.get(targetClass);
if (map == null) {
Field[] fields = targetClass.getDeclaredFields();
map = Maps.newHashMapWithExpectedSize(fields.length);
for (Field field : fields) {
CommandParameter annotation = field.getAnnotation(CommandParameter.class);
if (annotation != null && !annotation.value().isEmpty()) {
map.put(annotation.value(), field.getName());
}
}
definitionsCache.putIfAbsent(targetClass, map);
return map;
} else {
return map;
}
}
/**
* Copied from WebDataBinder.
*
* @param multipartFiles
* @param mpvs
*/
protected void bindMultipart(Map<String, List<MultipartFile>> multipartFiles, MutablePropertyValues mpvs) {
for (Map.Entry<String, List<MultipartFile>> entry : multipartFiles.entrySet()) {
String key = entry.getKey();
List<MultipartFile> values = entry.getValue();
if (values.size() == 1) {
MultipartFile value = values.get(0);
if (!value.isEmpty()) {
mpvs.add(key, value);
}
} else {
mpvs.add(key, values);
}
}
}
}
And then registering the parameter resolver using a post-processor. It should be registered as a <bean>:
/**
* Post-processor to be used if any modifications to the handler adapter need to be made
*
* @author bozho
*
*/
public class AnnotationHandlerMappingPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessAfterInitialization(Object bean, String arg1)
throws BeansException {
return bean;
}
@Override
public Object postProcessBeforeInitialization(Object bean, String arg1)
throws BeansException {
if (bean instanceof RequestMappingHandlerAdapter) {
RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter) bean;
List<HandlerMethodArgumentResolver> resolvers = adapter.getCustomArgumentResolvers();
if (resolvers == null) {
resolvers = Lists.newArrayList();
}
resolvers.add(new AnnotationServletModelAttributeResolver(false));
adapter.setCustomArgumentResolvers(resolvers);
}
return bean;
}
}