Example usage for org.springframework.core MethodParameter isOptional

Introduction

In this page you can find the example usage for org.springframework.core MethodParameter isOptional.

Prototype

public boolean isOptional() 

Source Link

Document

Return whether this method indicates a parameter which is not required: either in the form of Java 8's java.util.Optional , any variant of a parameter-level Nullable annotation (such as from JSR-305 or the FindBugs set of annotations), or a language-level nullable type declaration in Kotlin.

Usage

From source file:org.springframework.web.method.annotation.ModelAttributeMethodProcessor.java

/**
 * Construct a new attribute instance with the given constructor.
 * <p>Called from/*from www.j av  a 2  s  .  c  o m*/
 * {@link #createAttribute(String, MethodParameter, WebDataBinderFactory, NativeWebRequest)}
 * after constructor resolution.
 * @param ctor the constructor to use
 * @param attributeName the name of the attribute (never {@code null})
 * @param binderFactory for creating WebDataBinder instance
 * @param webRequest the current request
 * @return the created model attribute (never {@code null})
 * @throws BindException in case of constructor argument binding failure
 * @throws Exception in case of constructor invocation failure
 * @since 5.0
 */
protected Object constructAttribute(Constructor<?> ctor, String attributeName,
        WebDataBinderFactory binderFactory, NativeWebRequest webRequest) throws Exception {

    if (ctor.getParameterCount() == 0) {
        // A single default constructor -> clearly a standard JavaBeans arrangement.
        return BeanUtils.instantiateClass(ctor);
    }

    // A single data class constructor -> resolve constructor arguments from request parameters.
    ConstructorProperties cp = ctor.getAnnotation(ConstructorProperties.class);
    String[] paramNames = (cp != null ? cp.value() : parameterNameDiscoverer.getParameterNames(ctor));
    Assert.state(paramNames != null, () -> "Cannot resolve parameter names for constructor " + ctor);
    Class<?>[] paramTypes = ctor.getParameterTypes();
    Assert.state(paramNames.length == paramTypes.length,
            () -> "Invalid number of parameter names: " + paramNames.length + " for constructor " + ctor);

    Object[] args = new Object[paramTypes.length];
    WebDataBinder binder = binderFactory.createBinder(webRequest, null, attributeName);
    String fieldDefaultPrefix = binder.getFieldDefaultPrefix();
    String fieldMarkerPrefix = binder.getFieldMarkerPrefix();
    boolean bindingFailure = false;

    for (int i = 0; i < paramNames.length; i++) {
        String paramName = paramNames[i];
        Class<?> paramType = paramTypes[i];
        Object value = webRequest.getParameterValues(paramName);
        if (value == null) {
            if (fieldDefaultPrefix != null) {
                value = webRequest.getParameter(fieldDefaultPrefix + paramName);
            }
            if (value == null && fieldMarkerPrefix != null) {
                if (webRequest.getParameter(fieldMarkerPrefix + paramName) != null) {
                    value = binder.getEmptyValue(paramType);
                }
            }
        }
        try {
            MethodParameter methodParam = new MethodParameter(ctor, i);
            if (value == null && methodParam.isOptional()) {
                args[i] = (methodParam.getParameterType() == Optional.class ? Optional.empty() : null);
            } else {
                args[i] = binder.convertIfNecessary(value, paramType, methodParam);
            }
        } catch (TypeMismatchException ex) {
            ex.initPropertyName(paramName);
            binder.getBindingErrorProcessor().processPropertyAccessException(ex, binder.getBindingResult());
            bindingFailure = true;
            args[i] = value;
        }
    }

    if (bindingFailure) {
        if (binder.getBindingResult() instanceof AbstractBindingResult) {
            AbstractBindingResult result = (AbstractBindingResult) binder.getBindingResult();
            for (int i = 0; i < paramNames.length; i++) {
                result.recordFieldValue(paramNames[i], paramTypes[i], args[i]);
            }
        }
        throw new BindException(binder.getBindingResult());
    }

    return BeanUtils.instantiateClass(ctor, args);
}

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