springMvc源码之@RequestParam参数绑定解析

作者: 后来丶_a24d | 来源:发表于2018-11-21 21:20 被阅读0次

问题点

Http 调用接口的时候请求参数(String类型)由于有一个值为null, 而需要绑定的参数为Integer类型故一直404
在类型转时调用了Integer.valueOf(str), 而从底层源码来看当传入参数为空时会直接抛出throw new NumberFormatException("null");

解决方案

处理掉请求参数的null值并找到为null的原因。

源码简化版时序图

springmvc参数转换以及controller调用

springmvc参数转换以及controller调用.jpg
springmvc绑定参数处理从1.1开始

springmvc绑定参数处理.jpg

对标spring源码

从DispatchServlet的doService()开始分析

DispatcherServlet

在doService方法中调用doDispatch方法，handlerAdapter开始调用controller中对应方法。

 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

RequestMappingHandlerAdapter

这个类是具体的处理url请求HandlerAdapter，其中调用到handleInternal()方法

继续调用invokeHandleMethod方法

return this.invokeHandleMethod(request, response, handlerMethod);

继续调用下一个类的invokeAndHandle()方法

ServletInvocableHandlerMethod[图片上传中...(springmvc绑定参数处理.jpg-7d2cfe-1548496536396-0)]

继承自InvocableHandlerMethod
查看对应的invokeAndHandle方法

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
        //下一个调用口， 父类的方法
        Object returnValue = this.invokeForRequest(webRequest, mavContainer, providedArgs);
        this.setResponseStatus(webRequest);
        if (returnValue == null) {
            if (this.isRequestNotModified(webRequest) || this.hasResponseStatus() || mavContainer.isRequestHandled()) {
                mavContainer.setRequestHandled(true);
                return;
            }
        } else if (StringUtils.hasText(this.responseReason)) {
            mavContainer.setRequestHandled(true);
            return;
        }

        mavContainer.setRequestHandled(false);

        try {
            this.returnValueHandlers.handleReturnValue(returnValue, this.getReturnValueType(returnValue), mavContainer, webRequest);
        } catch (Exception var6) {
            if (this.logger.isTraceEnabled()) {
                this.logger.trace(this.getReturnValueHandlingErrorMessage("Error handling return value", returnValue), var6);
            }

            throw var6;
        }
    }

InvocableHandlerMethod

上一个类调用父类的invokeForRequest方法, 在这个方法中解决完参数绑定问题之后调用对应方法。

public Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer,
            Object... providedArgs) throws Exception {
                //下一个调用的方法 解决参数绑定的形参
        Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
        if (logger.isTraceEnabled()) {
            StringBuilder sb = new StringBuilder("Invoking [");
            sb.append(getBeanType().getSimpleName()).append(".");
            sb.append(getMethod().getName()).append("] method with arguments ");
            sb.append(Arrays.asList(args));
            logger.trace(sb.toString());
        }
//反射调用
        Object returnValue = doInvoke(args);
        if (logger.isTraceEnabled()) {
            logger.trace("Method [" + getMethod().getName() + "] returned [" + returnValue + "]");
        }
        return returnValue;
    }

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(this.parameterNameDiscoverer);
            GenericTypeResolver.resolveParameterType(parameter, getBean().getClass());
            args[i] = resolveProvidedArgument(parameter, providedArgs);
            if (args[i] != null) {
                continue;
            }
            if (this.argumentResolvers.supportsParameter(parameter)) {
                try {
                    //下一个类调用的方法
                    args[i] = this.argumentResolvers.resolveArgument(
                            parameter, mavContainer, request, this.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;
    }

HandlerMethodArgumentResolverComposite

继承自HandlerMethodArgumentResolver

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() + "]");
//下一个要调用的方法
        return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
    }

AbstractNamedValueMethodArgumentResolver

继承自HandlerMethodArgumentResolver
用于从指定值解析方法参数的抽象基类. Request parameters, request headers, and path variables这些

public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
            NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {

        Class<?> paramType = parameter.getParameterType();
        NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);

        Object arg = resolveName(namedValueInfo.name, parameter, webRequest);
        if (arg == null) {
            if (namedValueInfo.defaultValue != null) {
                arg = resolveDefaultValue(namedValueInfo.defaultValue);
            }
            else if (namedValueInfo.required && !parameter.getParameterType().getName().equals("java.util.Optional")) {
                handleMissingValue(namedValueInfo.name, parameter);
            }
            arg = handleNullValue(namedValueInfo.name, arg, paramType);
        }
        else if ("".equals(arg) && namedValueInfo.defaultValue != null) {
            arg = resolveDefaultValue(namedValueInfo.defaultValue);
        }

        if (binderFactory != null) {
            WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);
                      //下一个要调用的方法
            arg = binder.convertIfNecessary(arg, paramType, parameter);
        }

        handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest);

        return arg;
    }

DataBinder

implements PropertyEditorRegistry, TypeConverter
数据绑定,把HttpServletRequest中的数据纳入到Spring的管理。
将参数类型和请求数据再发给TypeConverter，由TypeConverter装配成一个bean。
TypeConverter将装配好的bean返回给DataBinder
DataBinder将装配bean交给处理请求的方法。

public <T> T convertIfNecessary(Object value, Class<T> requiredType, MethodParameter methodParam)
            throws TypeMismatchException {
                  
        return getTypeConverter().convertIfNecessary(value, requiredType, methodParam);
    }

TypeConverterSupport

类型转换的实现，持有一个TypeConverterDelegate，具体转换工作交给TypeConverterDelegate完成.
extends PropertyEditorRegistrySupport implements TypeConverter

public <T> T convertIfNecessary(Object value, Class<T> requiredType, MethodParameter methodParam)
            throws TypeMismatchException {

        return doConvert(value, requiredType, methodParam, null);
    }

private <T> T doConvert(Object value, Class<T> requiredType, MethodParameter methodParam, Field field)
            throws TypeMismatchException {
        try {
//下一个
            if (field != null) {
                return this.typeConverterDelegate.convertIfNecessary(value, requiredType, field);
            }
            else {
                return this.typeConverterDelegate.convertIfNecessary(value, requiredType, methodParam);
            }
        }
        catch (ConverterNotFoundException ex) {
            throw new ConversionNotSupportedException(value, requiredType, ex);
        }
        catch (ConversionException ex) {
            throw new TypeMismatchException(value, requiredType, ex);
        }
        catch (IllegalStateException ex) {
            throw new ConversionNotSupportedException(value, requiredType, ex);
        }
        catch (IllegalArgumentException ex) {
            throw new TypeMismatchException(value, requiredType, ex);
        }
    }

TypeConverterDelegate

单独的类

public <T> T convertIfNecessary(Object newValue, Class<T> requiredType, MethodParameter methodParam)
            throws IllegalArgumentException {

        return convertIfNecessary(null, null, newValue, requiredType,
                (methodParam != null ? new TypeDescriptor(methodParam) : TypeDescriptor.valueOf(requiredType)));
    }

public <T> T convertIfNecessary(String propertyName, Object oldValue, Object newValue,
            Class<T> requiredType, TypeDescriptor typeDescriptor) throws IllegalArgumentException {

        Object convertedValue = newValue;

        // Custom editor for this type?
        PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);

        ConversionFailedException firstAttemptEx = null;

        // No custom editor but custom ConversionService specified?
        ConversionService conversionService = this.propertyEditorRegistry.getConversionService();
        if (editor == null && conversionService != null && convertedValue != null && typeDescriptor != null) {
            TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
            TypeDescriptor targetTypeDesc = typeDescriptor;
            if (conversionService.canConvert(sourceTypeDesc, targetTypeDesc)) {
                try {
//下一个
                    return (T) conversionService.convert(convertedValue, sourceTypeDesc, targetTypeDesc);
                }
                catch (ConversionFailedException ex) {
                    // fallback to default conversion logic below
                    firstAttemptEx = ex;
                }
            }
        }

        。。。。

GenericConversionService

implements ConfigurableConversionService

public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
        Assert.notNull(targetType, "targetType to convert to cannot be null");
        if (sourceType == null) {
            Assert.isTrue(source == null, "source must be [null] if sourceType == [null]");
            return handleResult(null, targetType, convertNullSource(null, targetType));
        }
        if (source != null && !sourceType.getObjectType().isInstance(source)) {
            throw new IllegalArgumentException("source to convert from must be an instance of " +
                    sourceType + "; instead it was a " + source.getClass().getName());
        }
        GenericConverter converter = getConverter(sourceType, targetType);
        if (converter != null) {
//下一个
            Object result = ConversionUtils.invokeConverter(converter, source, sourceType, targetType);
            return handleResult(sourceType, targetType, result);
        }
        return handleConverterNotFound(source, sourceType, targetType);
    }

ConversionUtils

public static Object invokeConverter(GenericConverter converter, Object source, TypeDescriptor sourceType,
            TypeDescriptor targetType) {
        try {
            return converter.convert(source, sourceType, targetType);
        }
        catch (ConversionFailedException ex) {
            throw ex;
        }
        catch (Exception ex) {
            throw new ConversionFailedException(sourceType, targetType, source, ex);
        }
    }

GenericConversionService的内部类ConverterFactoryAdapter中convert

public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
            if (source == null) {
                return convertNullSource(sourceType, targetType);
            }
            return this.converterFactory.getConverter(targetType.getObjectType()).convert(source);
        }

StringToNumberConverterFactory的内部StringToNumberConverterFactory

-　implements ConverterFactory<String, Number>

public <T extends Number> Converter<String, T> getConverter(Class<T> targetType) {
        return new StringToNumber<T>(targetType);
    }

public T convert(String source) {
            if (source.length() == 0) {
                return null;
            }
            return NumberUtils.parseNumber(source, this.targetType);
        }

NumberUtils

public static <T extends Number> T parseNumber(String text, Class<T> targetClass) {
        Assert.notNull(text, "Text must not be null");
        Assert.notNull(targetClass, "Target class must not be null");
        String trimmed = StringUtils.trimAllWhitespace(text);

        if (targetClass.equals(Byte.class)) {
            return (T) (isHexNumber(trimmed) ? Byte.decode(trimmed) : Byte.valueOf(trimmed));
        }
        else if (targetClass.equals(Short.class)) {
            return (T) (isHexNumber(trimmed) ? Short.decode(trimmed) : Short.valueOf(trimmed));
        }
        else if (targetClass.equals(Integer.class)) {
            return (T) (isHexNumber(trimmed) ? Integer.decode(trimmed) : Integer.valueOf(trimmed));
        }
        else if (targetClass.equals(Long.class)) {
            return (T) (isHexNumber(trimmed) ? Long.decode(trimmed) : Long.valueOf(trimmed));
        }
        else if (targetClass.equals(BigInteger.class)) {
            return (T) (isHexNumber(trimmed) ? decodeBigInteger(trimmed) : new BigInteger(trimmed));
        }
        else if (targetClass.equals(Float.class)) {
            return (T) Float.valueOf(trimmed);
        }
        else if (targetClass.equals(Double.class)) {
            return (T) Double.valueOf(trimmed);
        }
        else if (targetClass.equals(BigDecimal.class) || targetClass.equals(Number.class)) {
            return (T) new BigDecimal(trimmed);
        }
        else {
            throw new IllegalArgumentException(
                    "Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
        }
    }

参考文章

https://www.cnblogs.com/wewill/p/5676920.html

springMvc源码之@RequestParam参数绑定解析

问题点

解决方案

源码简化版时序图

对标spring源码

DispatcherServlet

RequestMappingHandlerAdapter

ServletInvocableHandlerMethod[图片上传中...(springmvc绑定参数处理.jpg-7d2cfe-1548496536396-0)]

InvocableHandlerMethod

HandlerMethodArgumentResolverComposite

AbstractNamedValueMethodArgumentResolver

DataBinder

TypeConverterSupport

TypeConverterDelegate

GenericConversionService

ConversionUtils

GenericConversionService的内部类ConverterFactoryAdapter中convert

StringToNumberConverterFactory的内部StringToNumberConverterFactory

NumberUtils

参考文章

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