JAN ORM

JAN ORM Description

JAN ORM is a Java based lightweight Object Relational Mapper used for connection to a PostGreSQL Database without the need for SQL or Connection Management.

Authors: Jack Welsh, Aron Jang, Nate Opsal
Date Last Updated: 06/27/2021

TechStack

Java - version 8.0
JUnit - version 42.2.12
Apache Maven - version 3.8.1
PostGreSQL - deployed on AWS RDS
Git Source Code Management (on GitHub)

Features

Ready to Use

Drop then create a table from on an annotated class
Save an instance of an object from the table as an object
Update an entry in the database
Delete an entry from the database
Find entries in the database that satisfy given columns, operands, and values
Add given constraint on columns using annotations
- Primary Key
- Foreign Key
- Check
- Unique
- Default Value
- Not Null
Basic Caching
The Following SQL Aggregate Functions:
- Count
Transaction Control

Future Devlopement

Second-Level Caching
Implementing Complex Queries
Implementing Stored Procedures
The Following SQL Aggregate Functions:
- Sum
- Min
- Max
- Avg

Getting Started

Clone the Application

  git clone <this-repo>

Place Dependency Inside Your Project pom.xml File

  <dependency>
    <groupId>com.revature</groupId>
    <artifactId>JAN_ORM_p1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </dependency>

Add connection.properties file

Ensure that you have created this file in src/main/resources/ and have the following lines of code:

 url=path/to/database
 username=username_for_database
 password=password_for_database

Usage

Annotating Classes to Persist to Database

For a class to be persisted to the database, it must be a JavaBean and annotated using the following annotations:

Annotation	Purpose
@Table(name = "table_name")	Indicates to the ORM that this class is associated with table 'table_name'
@Column()	Indicates to the ORM that this field is a column in the table. The column name is automatically the field name.
@PrimaryKey	Indicates to the ORM that this field is a Prmary key Each class can only have one primary key.
@ForeignKey(refColumn = "ref_field", refClass = "ref_class")	Indicates to the ORM that this field is a Foreign Key that references class 'ref_class' and its field 'ref_field'
@CheckColumn(checkStmt = "check_statement")	Indicates to the ORM that this field is must undergo the "check_statement" before the record can be added to the table
@NotNull()	Indicates to the ORM that this field cannot be null
@DefaultValue(defaultValue = "default_value")	Indicates to the ORM that if no value is given for this field, then the default value will populate the field
@Unique()	Indicates to the ORM that this field has to be unique and cannot contain multiples of the same value in the table

User API

ObjectMapper Class

Used to Create Tables from Classes

ObjectMapper Class Method	Purpose
public static void addToModel(Class<?> c)	Adds the annotated class to the a local model of classes
public static boolean removeFromModel(Class<?> c)	Removes the annotated class from the local model of classes
public static boolean removeFromDB(Class<?> c, boolean cascadeDelete)	Removes the annotated class from the local model of classes and from the database
public static void buildDBFromModel()	Creates tables in the database from the local model of classes

ObjectQuery Class

Used to query the database

ObjectQuery Class Method	Purpose
public static void addObjectToTable(Object obj)	Adds the object to the database table. Must use the ObjectMapper Methods first to create the table before adding Object to Database
public static List<Object> returnAllObjectsFromTable( String tableName)	Returns a List of All Objects From the Table Query: SELECT FROM tableName;*
public static List<Object> returnObjectsWhereColumnIs( String tableName, String ColumnName, String Value)	Returns a List of Objects where the condition is met Query: SELECT FROM tableName WHERE ColumnName = Value;*
public static List<Object> returnObjectsWhereColumnIsLessThan( String tableName, String ColumnName, String Value)	Returns a List of Objects where the condition is met Query: SELECT FROM tableName WHERE ColumnName < Value;*
public static List<Object> returnObjectsWhereColumnIsGreaterThan( String tableName, String ColumnName, String Value)	Returns a List of Objects where the condition is met Query: SELECT FROM tableName WHERE ColumnName > Value;*
public static List<Object> returnObjectsWhere2ColumnsAre( String tableName, String ColumnName, String Value, String ColumnName2, String Value2)	Returns a List of Objects where two condition are met Query: SELECT FROM tableName WHERE ColumnName = Value AND ColumnName2 = Value2;*
public static List<Object> returnObjectsWhereColumnsAre( String tableName, String[] ColumnNames, String[] Operands, String[] Values)	Returns a List of Objects where columnNames.length conditions are met Query: SELECT FROM tableName WHERE ColumnName[0] Operand[0] Value[0] AND ColumnName[1] Operand[1] Value[1] AND ... ColumnName[n] Operand[n] Value[n];*
public static int returnCountOfObjectsWhereColumnIs( String tableName, String ColumnName, String Value)	Returns Count of the number of objects in the database where the condition is met Query: SELECT COUNT(ColumnName) FROM tableName WHERE ColumnName = Value;
public static int returnCountOfObjectsWhereColumnIsLessThan( String tableName, String ColumnName, String Value)	Returns Count of the number of objects in the database where the condition is met Query: SELECT COUNT(ColumnName) FROM tableName WHERE ColumnName <> Value;
public static int returnCountOfObjectsWhereColumnIsGreaterThan( String tableName, String ColumnName, String Value)	Returns Count of the number of objects in the database where the condition is met Query: SELECT COUNT(ColumnName) FROM tableName WHERE ColumnName > Value;
public static void removeObjectFromTable( Object obj, String tableName)	Removes given object from the database Query: DELETE FROM tableName WHERE id = obj.Id;
public static void truncateTable(String tableName)	Truncates given table in the database Query: TRUNCATE TABLE tableName;
public static void udpateAllWhere ( String tableName, String columnName, String oldValue, String newValue)	Updates all values in the given column that match oldValue to newValue Query: UPDATE tableName SET columnName = newValue WHERE columnName = oldValue;
public static void updateObjectToTable(Object newObj)	Updates the object in the database to the values passed in the the newObj. Object to be updated is based on the primary key value. Query: UPDATE tableName SET column1 = value1, column2 = value2,... WHERE id = newObj.Id;
public static ObjectCache getCache()	Used to get an ObjectCache object to perform ObjectCache methods

ObjectCache Class

Used to query the Cache
To get a cache Object, use ObjectQuery.getCache()

ObjectCache Class Method	Purpose
public void addObjectToCache(Object obj)	Adds Object obj to the Cache
public void deleteObjectFromCache(Object obj)	Deletes Object obj from the Cache
public HashSet<Object> getAllObjectsInCache(Class<?> clazz)	Gets all objects of Class clazz from the Cache and returns in a HashSet
public void deleteAllObjectsInCache(Class<?> clazz)	Deletes all objects of Class clazz fromthe Cache

DatabaseTransaction Class

Used to set Transactions the Database
A Transaction must start with beginTransaction() and end with commitTransaction()

DatabaseTransaction Class Method	Purpose
public static void beginTransaction()	Used to begin a Transaction Query: BEGIN;
public static void commitTransaction()	Used to commit a Transaction Query: COMMIT;
public static void setSavepoint(String SavePointName)	Used to set a Transaction Save Point Query: SAVEPOINT SavePointName;
public static void rollbackToSavepoint(String SavePointName)	Used to begin a Transaction Query: ROLLBACK TO SAVEPOINT SavePointName;
public static void rollbackTransaction()	Used to begin a Transaction Query: ROLLBACK;