Spring DataBinder

两种构造方式创建数据绑定组件：

/**
 * Create a new DataBinder instance, with default object name.
 * @param target the target object to bind onto (or {@code null}
 * if the binder is just used to convert a plain parameter value)
 * @see #DEFAULT_OBJECT_NAME
 */
public DataBinder(@Nullable Object target) {
	this(target, DEFAULT_OBJECT_NAME);
}

/**
 * Create a new DataBinder instance.
 * @param target the target object to bind onto (or {@code null}
 * if the binder is just used to convert a plain parameter value)
 * @param objectName the name of the target object
 */
public DataBinder(@Nullable Object target, String objectName) {
	this.target = ObjectUtils.unwrapOptional(target);
	this.objectName = objectName;
}

　　

说明：

or null if the binder is just used to convert a plain parameter value【 如果仅使用数据绑定组件的类型转换功能，则可以将target对象设置为null。】

类型转换功能（实现了TypeConvert[org.springframework.beans.TypeConverter]接口，因此拥有类型转换功能）：　　

@Nullable
 T convertIfNecessary(@Nullable Object value, @Nullable Class requiredType) throws TypeMismatchException;

@Nullable
 T convertIfNecessary(@Nullable Object value, @Nullable Class requiredType,
		@Nullable MethodParameter methodParam) throws TypeMismatchException;

@Nullable
 T convertIfNecessary(@Nullable Object value, @Nullable Class requiredType, @Nullable Field field)
		throws TypeMismatchException;

@Nullable
default  T convertIfNecessary(@Nullable Object value, @Nullable Class requiredType,
		@Nullable TypeDescriptor typeDescriptor) throws TypeMismatchException {

	throw new UnsupportedOperationException("TypeDescriptor resolution not supported");
}

　　

使用方式：

DataBinder db = new DataBinder(null);

Integer s = db.convertIfNecessary("324", Integer.class);
Double aDouble = db.convertIfNecessary("234.32", Double.class);
Integer integer = db.convertIfNecessary(1232.633, Integer.class);
Integer[] integers = db.convertIfNecessary(new String[]{"123", "456"}, Integer[].class);