/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.validation;

import java.util.List;

import org.springframework.beans.PropertyAccessor;
import org.springframework.lang.Nullable;

Stores and exposes information about data-binding and validation
errors for a specific object.
Field names can be properties of the target object (e.g. "name" when binding to a customer object), or nested fields in case of subobjects (e.g. "address.street"). Supports subtree navigation via setNestedPath(String): for example, an AddressValidator validates "address", not being aware that this is a subobject of customer. 
Note: Errors objects are single-threaded. 
Author:
Rod Johnson, Juergen Hoeller
See Also:
setNestedPath
BindException
DataBinder
ValidationUtils/**
 * Stores and exposes information about data-binding and validation
 * errors for a specific object.
 *
 * <p>Field names can be properties of the target object (e.g. "name"
 * when binding to a customer object), or nested fields in case of
 * subobjects (e.g. "address.street"). Supports subtree navigation
 * via {@link #setNestedPath(String)}: for example, an
 * {@code AddressValidator} validates "address", not being aware
 * that this is a subobject of customer.
 *
 * <p>Note: {@code Errors} objects are single-threaded.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setNestedPath
 * @see BindException
 * @see DataBinder
 * @see ValidationUtils
 */
public interface Errors {

	
The separator between path elements in a nested path,
for example in "customer.name" or "customer.address.street".
"." = same as the nested property separator in the beans package. /**
	 * The separator between path elements in a nested path,
	 * for example in "customer.name" or "customer.address.street".
	 * <p>"." = same as the
	 * {@link org.springframework.beans.PropertyAccessor#NESTED_PROPERTY_SEPARATOR nested property separator}
	 * in the beans package.
	 */
	String NESTED_PATH_SEPARATOR = PropertyAccessor.NESTED_PROPERTY_SEPARATOR;


	
Return the name of the bound root object.
/**
	 * Return the name of the bound root object.
	 */
	String getObjectName();

	
Allow context to be changed so that standard validators can validate
subtrees. Reject calls prepend the given path to the field names.
For example, an address validator could validate the subobject
"address" of a customer object.
Params:
nestedPath – nested path within this object, e.g. "address" (defaults to "", null is also acceptable). Can end with a dot: both "address" and "address." are valid./**
	 * Allow context to be changed so that standard validators can validate
	 * subtrees. Reject calls prepend the given path to the field names.
	 * <p>For example, an address validator could validate the subobject
	 * "address" of a customer object.
	 * @param nestedPath nested path within this object,
	 * e.g. "address" (defaults to "", {@code null} is also acceptable).
	 * Can end with a dot: both "address" and "address." are valid.
	 */
	void setNestedPath(String nestedPath);

	
Return the current nested path of this Errors object. 
Returns a nested path with a dot, i.e. "address.", for easy
building of concatenated paths. Default is an empty String.
/**
	 * Return the current nested path of this {@link Errors} object.
	 * <p>Returns a nested path with a dot, i.e. "address.", for easy
	 * building of concatenated paths. Default is an empty String.
	 */
	String getNestedPath();

	
Push the given sub path onto the nested path stack.
A popNestedPath() call will reset the original nested path before the corresponding pushNestedPath(String) call. 
Using the nested path stack allows to set temporary nested paths
for subobjects without having to worry about a temporary path holder.
For example: current path "spouse.", pushNestedPath("child") ->
result path "spouse.child."; popNestedPath() -> "spouse." again.
Params:
subPath – the sub path to push onto the nested path stack
See Also:
popNestedPath/**
	 * Push the given sub path onto the nested path stack.
	 * <p>A {@link #popNestedPath()} call will reset the original
	 * nested path before the corresponding
	 * {@code pushNestedPath(String)} call.
	 * <p>Using the nested path stack allows to set temporary nested paths
	 * for subobjects without having to worry about a temporary path holder.
	 * <p>For example: current path "spouse.", pushNestedPath("child") ->
	 * result path "spouse.child."; popNestedPath() -> "spouse." again.
	 * @param subPath the sub path to push onto the nested path stack
	 * @see #popNestedPath
	 */
	void pushNestedPath(String subPath);

	
Pop the former nested path from the nested path stack.
Throws:
IllegalStateException – if there is no former nested path on the stack
See Also:
pushNestedPath/**
	 * Pop the former nested path from the nested path stack.
	 * @throws IllegalStateException if there is no former nested path on the stack
	 * @see #pushNestedPath
	 */
	void popNestedPath() throws IllegalStateException;

	
Register a global error for the entire target object,
using the given error description.
Params:
errorCode – error code, interpretable as a message key/**
	 * Register a global error for the entire target object,
	 * using the given error description.
	 * @param errorCode error code, interpretable as a message key
	 */
	void reject(String errorCode);

	
Register a global error for the entire target object,
using the given error description.
Params:
errorCode – error code, interpretable as a message key
defaultMessage – fallback default message/**
	 * Register a global error for the entire target object,
	 * using the given error description.
	 * @param errorCode error code, interpretable as a message key
	 * @param defaultMessage fallback default message
	 */
	void reject(String errorCode, String defaultMessage);

	
Register a global error for the entire target object,
using the given error description.
Params:
errorCode – error code, interpretable as a message key
errorArgs – error arguments, for argument binding via MessageFormat (can be null)
defaultMessage – fallback default message/**
	 * Register a global error for the entire target object,
	 * using the given error description.
	 * @param errorCode error code, interpretable as a message key
	 * @param errorArgs error arguments, for argument binding via MessageFormat
	 * (can be {@code null})
	 * @param defaultMessage fallback default message
	 */
	void reject(String errorCode, @Nullable Object[] errorArgs, @Nullable String defaultMessage);

	
Register a field error for the specified field of the current object
(respecting the current nested path, if any), using the given error
description.
The field name may be null or empty String to indicate the current object itself rather than a field of it. This may result in a corresponding field error within the nested object graph or a global error if the current object is the top object. 
Params:
field – the field name (may be null or empty String)
errorCode – error code, interpretable as a message key
See Also:
getNestedPath()/**
	 * Register a field error for the specified field of the current object
	 * (respecting the current nested path, if any), using the given error
	 * description.
	 * <p>The field name may be {@code null} or empty String to indicate
	 * the current object itself rather than a field of it. This may result
	 * in a corresponding field error within the nested object graph or a
	 * global error if the current object is the top object.
	 * @param field the field name (may be {@code null} or empty String)
	 * @param errorCode error code, interpretable as a message key
	 * @see #getNestedPath()
	 */
	void rejectValue(@Nullable String field, String errorCode);

	
Register a field error for the specified field of the current object
(respecting the current nested path, if any), using the given error
description.
The field name may be null or empty String to indicate the current object itself rather than a field of it. This may result in a corresponding field error within the nested object graph or a global error if the current object is the top object. 
Params:
field – the field name (may be null or empty String)
errorCode – error code, interpretable as a message key
defaultMessage – fallback default message
See Also:
getNestedPath()/**
	 * Register a field error for the specified field of the current object
	 * (respecting the current nested path, if any), using the given error
	 * description.
	 * <p>The field name may be {@code null} or empty String to indicate
	 * the current object itself rather than a field of it. This may result
	 * in a corresponding field error within the nested object graph or a
	 * global error if the current object is the top object.
	 * @param field the field name (may be {@code null} or empty String)
	 * @param errorCode error code, interpretable as a message key
	 * @param defaultMessage fallback default message
	 * @see #getNestedPath()
	 */
	void rejectValue(@Nullable String field, String errorCode, String defaultMessage);

	
Register a field error for the specified field of the current object
(respecting the current nested path, if any), using the given error
description.
The field name may be null or empty String to indicate the current object itself rather than a field of it. This may result in a corresponding field error within the nested object graph or a global error if the current object is the top object. 
Params:
field – the field name (may be null or empty String)
errorCode – error code, interpretable as a message key
errorArgs – error arguments, for argument binding via MessageFormat (can be null)
defaultMessage – fallback default message
See Also:
getNestedPath()/**
	 * Register a field error for the specified field of the current object
	 * (respecting the current nested path, if any), using the given error
	 * description.
	 * <p>The field name may be {@code null} or empty String to indicate
	 * the current object itself rather than a field of it. This may result
	 * in a corresponding field error within the nested object graph or a
	 * global error if the current object is the top object.
	 * @param field the field name (may be {@code null} or empty String)
	 * @param errorCode error code, interpretable as a message key
	 * @param errorArgs error arguments, for argument binding via MessageFormat
	 * (can be {@code null})
	 * @param defaultMessage fallback default message
	 * @see #getNestedPath()
	 */
	void rejectValue(@Nullable String field, String errorCode,
			@Nullable Object[] errorArgs, @Nullable String defaultMessage);

	
Add all errors from the given Errors instance to this Errors instance. 
This is a convenience method to avoid repeated reject(..) calls for merging an Errors instance into another Errors instance. 
Note that the passed-in Errors instance is supposed to refer to the same target object, or at least contain compatible errors that apply to the target object of this Errors instance. 
Params:
errors – the Errors instance to merge in/**
	 * Add all errors from the given {@code Errors} instance to this
	 * {@code Errors} instance.
	 * <p>This is a convenience method to avoid repeated {@code reject(..)}
	 * calls for merging an {@code Errors} instance into another
	 * {@code Errors} instance.
	 * <p>Note that the passed-in {@code Errors} instance is supposed
	 * to refer to the same target object, or at least contain compatible errors
	 * that apply to the target object of this {@code Errors} instance.
	 * @param errors the {@code Errors} instance to merge in
	 */
	void addAllErrors(Errors errors);

	
Return if there were any errors.
/**
	 * Return if there were any errors.
	 */
	boolean hasErrors();

	
Return the total number of errors.
/**
	 * Return the total number of errors.
	 */
	int getErrorCount();

	
Get all errors, both global and field ones.
Returns:
a list of ObjectError instances/**
	 * Get all errors, both global and field ones.
	 * @return a list of {@link ObjectError} instances
	 */
	List<ObjectError> getAllErrors();

	
Are there any global errors?
See Also:
hasFieldErrors()
Returns:
true if there are any global errors/**
	 * Are there any global errors?
	 * @return {@code true} if there are any global errors
	 * @see #hasFieldErrors()
	 */
	boolean hasGlobalErrors();

	
Return the number of global errors.
See Also:
getFieldErrorCount()
Returns:
the number of global errors/**
	 * Return the number of global errors.
	 * @return the number of global errors
	 * @see #getFieldErrorCount()
	 */
	int getGlobalErrorCount();

	
Get all global errors.
Returns:
a list of ObjectError instances/**
	 * Get all global errors.
	 * @return a list of {@link ObjectError} instances
	 */
	List<ObjectError> getGlobalErrors();

	
Get the first global error, if any.
Returns:
the global error, or null/**
	 * Get the <i>first</i> global error, if any.
	 * @return the global error, or {@code null}
	 */
	@Nullable
	ObjectError getGlobalError();

	
Are there any field errors?
See Also:
hasGlobalErrors()
Returns:
true if there are any errors associated with a field/**
	 * Are there any field errors?
	 * @return {@code true} if there are any errors associated with a field
	 * @see #hasGlobalErrors()
	 */
	boolean hasFieldErrors();

	
Return the number of errors associated with a field.
See Also:
getGlobalErrorCount()
Returns:
the number of errors associated with a field/**
	 * Return the number of errors associated with a field.
	 * @return the number of errors associated with a field
	 * @see #getGlobalErrorCount()
	 */
	int getFieldErrorCount();

	
Get all errors associated with a field.
Returns:
a List of FieldError instances/**
	 * Get all errors associated with a field.
	 * @return a List of {@link FieldError} instances
	 */
	List<FieldError> getFieldErrors();

	
Get the first error associated with a field, if any.
Returns:
the field-specific error, or null/**
	 * Get the <i>first</i> error associated with a field, if any.
	 * @return the field-specific error, or {@code null}
	 */
	@Nullable
	FieldError getFieldError();

	
Are there any errors associated with the given field?
Params:
field – the field name
Returns:
true if there were any errors associated with the given field/**
	 * Are there any errors associated with the given field?
	 * @param field the field name
	 * @return {@code true} if there were any errors associated with the given field
	 */
	boolean hasFieldErrors(String field);

	
Return the number of errors associated with the given field.
Params:
field – the field name
Returns:
the number of errors associated with the given field/**
	 * Return the number of errors associated with the given field.
	 * @param field the field name
	 * @return the number of errors associated with the given field
	 */
	int getFieldErrorCount(String field);

	
Get all errors associated with the given field.
Implementations should support not only full field names like
"name" but also pattern matches like "na*" or "address.*".
Params:
field – the field name
Returns:
a List of FieldError instances/**
	 * Get all errors associated with the given field.
	 * <p>Implementations should support not only full field names like
	 * "name" but also pattern matches like "na*" or "address.*".
	 * @param field the field name
	 * @return a List of {@link FieldError} instances
	 */
	List<FieldError> getFieldErrors(String field);

	
Get the first error associated with the given field, if any.
Params:
field – the field name
Returns:
the field-specific error, or null/**
	 * Get the first error associated with the given field, if any.
	 * @param field the field name
	 * @return the field-specific error, or {@code null}
	 */
	@Nullable
	FieldError getFieldError(String field);

	
Return the current value of the given field, either the current
bean property value or a rejected update from the last binding.
Allows for convenient access to user-specified field values,
even if there were type mismatches.
Params:
field – the field name
Returns:
the current value of the given field/**
	 * Return the current value of the given field, either the current
	 * bean property value or a rejected update from the last binding.
	 * <p>Allows for convenient access to user-specified field values,
	 * even if there were type mismatches.
	 * @param field the field name
	 * @return the current value of the given field
	 */
	@Nullable
	Object getFieldValue(String field);

	
Return the type of a given field.
Implementations should be able to determine the type even when the field value is null, for example from some associated descriptor. 
Params:
field – the field name
Returns:
the type of the field, or null if not determinable/**
	 * Return the type of a given field.
	 * <p>Implementations should be able to determine the type even
	 * when the field value is {@code null}, for example from some
	 * associated descriptor.
	 * @param field the field name
	 * @return the type of the field, or {@code null} if not determinable
	 */
	@Nullable
	Class<?> getFieldType(String field);

}