io.jsondb

Class Util

java.lang.Object

io.jsondb.Util

public class Util
extends java.lang.Object

Constructor Summary

Constructors

Constructor and Description
Util()

Method Summary

Modifier and Type	Method and Description
protected static java.lang.Object	deepCopy(java.lang.Object fromBean) A utility method that creates a deep clone of the specified object.
static void	delete(java.io.File f) Utility to delete directory recursively
protected static java.lang.String	determineCollectionName(java.lang.Class<?> entityClass) A utility method to determine the collection name for a given entity class.
protected static <T> java.lang.String	determineEntityCollectionName(T obj)
protected static void	ensureNotRestricted(java.lang.Object o)
protected static java.lang.Object	getIdForEntity(java.lang.Object document, java.lang.reflect.Method getterMethodForId) A utility method to extract the value of field marked by the @Id annotation using its getter/accessor method.
static java.util.List<java.lang.Integer>	getSliceIndexes(java.lang.String slice, int size) Utility method to compute the indexes to select based on slice string
static boolean	isSliceable(java.lang.String slice)
protected static java.lang.Object	setFieldValueForEntity(java.lang.Object document, java.lang.Object newValue, java.lang.reflect.Method setterMethod)
protected static java.lang.Object	setIdForEntity(java.lang.Object document, java.lang.reflect.Method setterMethodForId) A utility method to set the value of field marked by the @Id annotation using its setter/mutator method.
static boolean	stampVersion(JsonDBConfig dbConfig, java.io.File f, java.lang.String version) Utility to stamp the version into a newly created .json File This method is expected to be invoked on a newly created .json file before it is usable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Util

public Util()

Method Detail

ensureNotRestricted

protected static void ensureNotRestricted(java.lang.Object o)

determineEntityCollectionName

protected static <T> java.lang.String determineEntityCollectionName(T obj)

determineCollectionName

protected static java.lang.String determineCollectionName(java.lang.Class<?> entityClass)

A utility method to determine the collection name for a given entity class. This method attempts to find a the annotation Document on this class. If found then we know the collection name else it throws a exception

Parameters:

entityClass - class that determines the name of the collection

Returns:

name of the class

getIdForEntity

protected static java.lang.Object getIdForEntity(java.lang.Object document,
                                                 java.lang.reflect.Method getterMethodForId)

A utility method to extract the value of field marked by the @Id annotation using its getter/accessor method.

Parameters:

document - the actual Object representing the POJO we want the Id of.

getterMethodForId - the Method that is the accessor for the attributed with @Id annotation

Returns:

the actual Id or if none exists then a new random UUID

setIdForEntity

protected static java.lang.Object setIdForEntity(java.lang.Object document,
                                                 java.lang.reflect.Method setterMethodForId)

A utility method to set the value of field marked by the @Id annotation using its setter/mutator method. TODO: Some day we want to support policies for generation of ID like AutoIncrement etc.

Parameters:

document - the actual Object representing the POJO we want the Id to be set for.

setterMethodForId - the Method that is the mutator for the attributed with @Id annotation

Returns:

the Id that was generated and set

setFieldValueForEntity

protected static java.lang.Object setFieldValueForEntity(java.lang.Object document,
                                                         java.lang.Object newValue,
                                                         java.lang.reflect.Method setterMethod)

deepCopy

protected static java.lang.Object deepCopy(java.lang.Object fromBean)

A utility method that creates a deep clone of the specified object. There is no other way of doing this reliably.

Parameters:

fromBean - java bean to be cloned.

Returns:

a new java bean cloned from fromBean.

stampVersion

public static boolean stampVersion(JsonDBConfig dbConfig,
                                   java.io.File f,
                                   java.lang.String version)

Utility to stamp the version into a newly created .json File This method is expected to be invoked on a newly created .json file before it is usable. So no locking code required.

Parameters:

dbConfig - all the settings used by Json DB

f - the target .json file on which to stamp the version

version - the actual version string to stamp

Returns:

true if success.

delete

public static void delete(java.io.File f)

Utility to delete directory recursively

Parameters:

f - File object representing the directory to recursively delete

isSliceable

public static boolean isSliceable(java.lang.String slice)

getSliceIndexes

public static java.util.List<java.lang.Integer> getSliceIndexes(java.lang.String slice,
                                                                int size)

Utility method to compute the indexes to select based on slice string

Parameters:

slice - select the indices in some slice_target list or array, should be a valid slice string The behaviour of this slicing feature is similar to the slicing feature in python or numpy, as much as possible https://docs.scipy.org/doc/numpy-1.13.0/reference/arrays.indexing.html A slice is a string notation and the basic slice syntax is i:j:k, where i is the starting index, j is the stopping index, and k is the step (k != 0). In other words it is start:stop:step Example slice_target = [T0, T1, T2, T3, T4, T5, T6, T7, T8, T9] slice = "1:7:2" returns [T1, T3, T5] i is inclusive, j is exclusive Negative i and j are interpreted as n + i and n + j where n is the number of elements found. Negative k makes stepping go towards smaller indices. Example slice_target = [T0, T1, T2, T3, T4, T5, T6, T7, T8, T9] slice = "-2:10" returns [T8, T9] slice = "-3:3:-1" returns [T7, T6, T5, T4] Assume n is the number of elements in slice_target. Then, if i is not given it defaults to 0 for k>0 and n - 1 for k<0 . If j is not given it defaults to n for k>0 and -n-1 for k<0 . If k is not given it defaults to 1. Note that :: is the same as : and means select all indices from slice_target. Example slice_target = [T0, T1, T2, T3, T4, T5, T6, T7, T8, T9] slice = "5:" returns [T5, T6, T7, T8, T9] Assume n is the number of elements in slice_target. Then, if j>n then it is considered as n, in case of negative j it is considered -n.

size - size of the array from which a slice is to extracted

Returns:

List of indexes to pick from the array to be returned