对于http://domain/path1/path2/mothod?k1=v1&k2=v2这种请求
对应的Controller方法为
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@RequestMapping("/path1/path2/mothod")
// model中含有k2属性
public ModelAndView mothod( String k1, Model model) {
return null;
}
那么Spring是如何把k1, k2的值是如何注入到相应的位置上呢?
Spring源码在:org.springframework.web.method.support.InvocableHandlerMethod
执行请求
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public final Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
StringBuilder builder = new StringBuilder("Invoking [");
builder.append(this.getMethod().getName()).append("] method with arguments ");
builder.append(Arrays.asList(args));
logger.trace(builder.toString());
}
Object returnValue = invoke(args);
if (logger.isTraceEnabled()) {
logger.trace("Method [" + this.getMethod().getName() + "] returned [" + returnValue + "]");
}
return returnValue;
}
解析参数列表
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private Object[] getMethodArgumentValues(NativeWebRequest request, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
MethodParameter[] parameters = getMethodParameters();
Object[] args = new Object[parameters.length];
for (int i = 0; i < parameters.length; i++) {
MethodParameter parameter = parameters[i];
parameter.initParameterNameDiscovery(parameterNameDiscoverer);
GenericTypeResolver.resolveParameterType(parameter, getBean().getClass());
args[i] = resolveProvidedArgument(parameter, providedArgs);
if (args[i] != null) {
continue;
}
if (argumentResolvers.supportsParameter(parameter)) {
try {
args[i] = argumentResolvers.resolveArgument(parameter, mavContainer, request, dataBinderFactory);
continue;
} catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(getArgumentResolutionErrorMessage("Error resolving argument", i), ex);
}
throw ex;
}
}
if (args[i] == null) {
String msg = getArgumentResolutionErrorMessage("No suitable resolver for argument", i);
throw new IllegalStateException(msg);
}
}
return args;
}
getMethodParameters(); 方法返回对应的Controller实现方法的参数列表, 然后对每个参数绑定(注入)数据 代码关键在于:args[i] = argumentResolvers.resolveArgument(parameter, mavContainer, request, dataBinderFactory);
获取每个参数值
可以看到, 对每种类型的参数, 获取方式在org.springframework.web.method.support.HandlerMethodArgumentResolverComposite,
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public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
Assert.notNull(resolver, "Unknown parameter type [" + parameter.getParameterType().getName() + "]");
return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
}
可以看到每种参数类型的处理逻辑是不同的, Spring通过HandlerMethodArgumentResolver接口实现了常见类型的处理逻辑 对于基本类型, 枚举类型调用: org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver实现 代码很简单, 基本上就是
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String[] paramValues = webRequest.getParameterValues(name);
if (paramValues != null) {
arg = paramValues.length == 1 ? paramValues[0] : paramValues;
}
对于自定义model调用: org.springframework.web.method.annotation.ModelAttributeMethodProcessor, org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor
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@Override
protected final Object createAttribute(String attributeName, MethodParameter parameter,
WebDataBinderFactory binderFactory, NativeWebRequest request) throws Exception {
String value = getRequestValueForAttribute(attributeName, request);
if (value != null) {
Object attribute = createAttributeFromRequestValue(value, attributeName, parameter, binderFactory, request);
if (attribute != null) {
return attribute;
}
}
return super.createAttribute(attributeName, parameter, binderFactory, request);
}
先从request中取出属性值, 如果不为空且有自定义类型转换服务, 把request中的返回的字符串按用户自定的类型转换实现进行解析
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protected Object createAttributeFromRequestValue(String sourceValue, String attributeName,
MethodParameter parameter, WebDataBinderFactory binderFactory, NativeWebRequest request) throws Exception {
DataBinder binder = binderFactory.createBinder(request, null, attributeName);
ConversionService conversionService = binder.getConversionService();
if (conversionService != null) {
TypeDescriptor source = TypeDescriptor.valueOf(String.class);
TypeDescriptor target = new TypeDescriptor(parameter);
if (conversionService.canConvert(source, target)) {
return binder.convertIfNecessary(sourceValue, parameter.getParameterType(), parameter);
}
}
return null;
}
如果为空, 则调用默认的数据绑定逻辑进行参数注入
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public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest request, WebDataBinderFactory binderFactory) throws Exception {
String name = ModelFactory.getNameForParameter(parameter);
Object attribute = (mavContainer.containsAttribute(name)) ?
mavContainer.getModel().get(name) : createAttribute(name, parameter, binderFactory, request);
WebDataBinder binder = binderFactory.createBinder(request, attribute, name);
if (binder.getTarget() != null) {
bindRequestParameters(binder, request);
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors()) {
if (isBindExceptionRequired(binder, parameter)) {
throw new BindException(binder.getBindingResult());
}
}
}
// Add resolved attribute and BindingResult at the end of the model
Map<String, Object> bindingResultModel = binder.getBindingResult().getModel();
mavContainer.removeAttributes(bindingResultModel);
mavContainer.addAllAttributes(bindingResultModel);
return binder.getTarget();
}
其中bindRequestParameters(binder, request);是关键
自定义类型转换
Spring3的类型转换接口实现逻辑如下:
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public class AndroidLoginContextConverter implements Converter<String, AndroidLoginContext> {
@Override
public AndroidLoginContext convert( String source ) {
return JSON.parseObject( source, AndroidLoginContext.class );
}
}
在context.xml中配置
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<bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="com.meizu.reader.web.android.AndroidLoginContextConverter"/>
</list>
</property>
</bean>
<bean id="webBindingInitializer" class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
<property name="conversionService" ref="conversionService"/>
</bean>
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
<property name="webBindingInitializer" ref="webBindingInitializer"/>
</bean>
然后对request需要做包装
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public class AndroidUserinfoRequestWrapper extends HttpServletRequestWrapper {
@Override
public String getParameter(String name) {
if( "androidLoginContext".equals( name ) ) {
return JSON.toJSONString( login );
}
String[] values = this.getParameterValues(name);
if (values == null) {
return null;
}
else {
return values[0];
}
}
}
其中如果参数类型为model对象, 参数名为类名的SimpleName, 首字母小写 如果为数据或者为集合, 则为类名的SimpleName+List
