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https://issues.apache.org/jira/browse/APEXMALHAR-1979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15120998#comment-15120998
]
Chinmay Kolhatkar commented on APEXMALHAR-1979:
-----------------------------------------------
h3. Objective
Objective of this utility is to provide a way to user to generate a compiled
and loadable bean class on the fly by providing schema of the bean in JSON
format.
h3. Usecase
Often it is required that the bean class to be used for transfer of data across
streams are not available at compiled time or the schema is provided to user
but not the class object of it.
This utility gives a way to use to create a compiled and directly loadable bean
class object by providing a simple JSON based schema.
In effect, the utility provides a way to bridge a gap between a schema
definition and a compiled bean class.
h3. Prereq/Requirements
org.apache.xbean:xbean-asm5-shaded
h3.Design/Functionality
Name of the utility class is com.datatorrent.lib.util.BeanClassGenerator which
provides the functionality. This will be part of malhar-library.
The class provides following functionality:
1. Generate a bean class object using simple JSON schema provided. Return a
bean class as a byte[].
2. Read the byte[] and fully qualified class name(fqcn) and return a Class
object for given fqcn.
The generation of class is done using asm5 library of apache xbean.
Schema definition using JSON will like following:
{code}
{
"fqcn":"<qualified class name>",
"fields": [
{
"name":"field1",
"type":"long"
},
{
"name":"field2",
"type": "java.lang.String"
}
]
}
{code}
Supported types identified in "type" JSON field are:
boolean, char, byte, short, int, float, long, double, any fqcn of java
object.
For eg.
- a String object in bean class should have type "java.lang.String".
- a int in bean class should have type "int"
Following methods will be added to the generated class:
a. Getter/Setter methods for given fields.
b. simple toString - Generate string equivalent for all the fields
c. hashCode method - calculate the overall hashCode using individual field
hashcodes, similar to how String.hashCode generates hashCode of string using
chars in it.
d. equals method - Similar to how String.equals method has done it using
individual char.
> Ability to generate compiled class from given json schema
> ---------------------------------------------------------
>
> Key: APEXMALHAR-1979
> URL: https://issues.apache.org/jira/browse/APEXMALHAR-1979
> Project: Apache Apex Malhar
> Issue Type: New Feature
> Reporter: Chinmay Kolhatkar
> Assignee: Chinmay Kolhatkar
>
> Ability to generate compiled class from given json schema.
> Will add the details on json schema soon.
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