类org.springframework.beans.factory.support.AbstractBeanFactory
方法T doGetBean(final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
这里requiredType是获取的实例要转换成的类型，转换通过org.springframework.beans.TypeConverter进行。
if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type [" +
ClassUtils.getQualifiedName(requiredType) + "]", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
类org.springframework.beans.TypeConverterDelegate
TypeConverter调用java.beans.PropertyEditor。
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 {
return (T) conversionService.convert(convertedValue, sourceTypeDesc, targetTypeDesc);
}
catch (ConversionFailedException ex) {
// fallback to default conversion logic below
firstAttemptEx = ex;
}
}
} // Value not of required type?
if (editor != null || (requiredType != null && !ClassUtils.isAssignableValue(requiredType, convertedValue))) {
if (requiredType != null && Collection.class.isAssignableFrom(requiredType) && convertedValue instanceof String) {
TypeDescriptor elementType = typeDescriptor.getElementTypeDescriptor();
if (elementType != null && Enum.class.isAssignableFrom(elementType.getType())) {
convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
}
}
if (editor == null) {
editor = findDefaultEditor(requiredType); // redis进入的是此分支路径
}
convertedValue = doConvertValue(oldValue, convertedValue, requiredType, editor);
} boolean standardConversion = false; if (requiredType != null) {
// Try to apply some standard type conversion rules if appropriate. if (convertedValue != null) {
if (Object.class.equals(requiredType)) {
return (T) convertedValue;
}
if (requiredType.isArray()) {
// Array required -> apply appropriate conversion of elements.
if (convertedValue instanceof String && Enum.class.isAssignableFrom(requiredType.getComponentType())) {
convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
}
return (T) convertToTypedArray(convertedValue, propertyName, requiredType.getComponentType());
}
else if (convertedValue instanceof Collection) {
// Convert elements to target type, if determined.
convertedValue = convertToTypedCollection(
(Collection<?>) convertedValue, propertyName, requiredType, typeDescriptor);
standardConversion = true;
}
else if (convertedValue instanceof Map) {
// Convert keys and values to respective target type, if determined.
convertedValue = convertToTypedMap(
(Map<?, ?>) convertedValue, propertyName, requiredType, typeDescriptor);
standardConversion = true;
}
if (convertedValue.getClass().isArray() && Array.getLength(convertedValue) == 1) {
convertedValue = Array.get(convertedValue, 0);
standardConversion = true;
}
if (String.class.equals(requiredType) && ClassUtils.isPrimitiveOrWrapper(convertedValue.getClass())) {
// We can stringify any primitive value...
return (T) convertedValue.toString();
}
else if (convertedValue instanceof String && !requiredType.isInstance(convertedValue)) {
if (firstAttemptEx == null && !requiredType.isInterface() && !requiredType.isEnum()) {
try {
Constructor<T> strCtor = requiredType.getConstructor(String.class);
return BeanUtils.instantiateClass(strCtor, convertedValue);
}
catch (NoSuchMethodException ex) {
// proceed with field lookup
if (logger.isTraceEnabled()) {
logger.trace("No String constructor found on type [" + requiredType.getName() + "]", ex);
}
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Construction via String failed for type [" + requiredType.getName() + "]", ex);
}
}
}
String trimmedValue = ((String) convertedValue).trim();
if (requiredType.isEnum() && "".equals(trimmedValue)) {
// It's an empty enum identifier: reset the enum value to null.
return null;
}
convertedValue = attemptToConvertStringToEnum(requiredType, trimmedValue, convertedValue);
standardConversion = true;
}
} if (!ClassUtils.isAssignableValue(requiredType, convertedValue)) {
if (firstAttemptEx != null) {
throw firstAttemptEx;
}
// Definitely doesn't match: throw IllegalArgumentException/IllegalStateException
StringBuilder msg = new StringBuilder();
msg.append("Cannot convert value of type [").append(ClassUtils.getDescriptiveType(newValue));
msg.append("] to required type [").append(ClassUtils.getQualifiedName(requiredType)).append("]");
if (propertyName != null) {
msg.append(" for property '").append(propertyName).append("'");
}
if (editor != null) {
msg.append(": PropertyEditor [").append(editor.getClass().getName()).append(
"] returned inappropriate value of type [").append(
ClassUtils.getDescriptiveType(convertedValue)).append("]");
throw new IllegalArgumentException(msg.toString());
}
else {
msg.append(": no matching editors or conversion strategy found");
throw new IllegalStateException(msg.toString());
}
}
} if (firstAttemptEx != null) {
if (editor == null && !standardConversion && requiredType != null && !Object.class.equals(requiredType)) {
throw firstAttemptEx;
}
logger.debug("Original ConversionService attempt failed - ignored since " +
"PropertyEditor based conversion eventually succeeded", firstAttemptEx);
} return (T) convertedValue;
}
类org.springframework.beans.BeanUtils
方法PropertyEditor findEditorByConvention(Class<?> targetType)
spring会自动获取type对应的editor
String editorName = targetType.getName() + "Editor";
try {
Class<?> editorClass = cl.loadClass(editorName);
if (!PropertyEditor.class.isAssignableFrom(editorClass)) {
if (logger.isWarnEnabled()) {
logger.warn("Editor class [" + editorName +
"] does not implement [java.beans.PropertyEditor] interface");
}
unknownEditorTypes.put(targetType, Boolean.TRUE);
return null;
}
return (PropertyEditor) instantiateClass(editorClass);
}
例如对org.springframework.data.redis.core.ListOperations则有org.springframework.data.redis.core.ListOperationsEditor
class ListOperationsEditor extends PropertyEditorSupport {
public void setValue(Object value) {
if (value instanceof RedisOperations) {
super.setValue(((RedisOperations) value).opsForList());
} else {
throw new java.lang.IllegalArgumentException("Editor supports only conversion of type " + RedisOperations.class);
}
}
}