Variable type processing of jbpm3

We know that the variable in the process definition is persistent, for example, it may be stored in the database. How can we deal with the type?
Let's take a look at the jbpm3 method:
Jbpm3 defines its own class jbpmtype, which has two attributes:
1) public class variableinstanceclass = NULL;
It indicates that the variable corresponds to the engine type.
2) Public converter = NULL;
It indicates the converter between the slave engine type and the Java type.

During processing, the engine first searches for the jbpm. type. properties file in the class path. If not
Search in the org/jbpm/DB/hibernate/jbpm. types. properties file. The file is edited as follows:
# Each line contains 2 or 3 class names (transformer-class is optional) separated by a space:
# Variable-class <space> transformer-class <space> variableinstance-class
# Or
# Variable-class <space> variableinstance-class

### Stored in a text-field in the database ###
Java. Lang. String org.jbpm.context.exe. variableinstance. stringinstance
Java. Lang. boolean org.jbpm.context.exe. converter. booleantostringconverter org.jbpm.context.exe. variableinstance. stringinstance
Java. Lang. Character org.jbpm.context.exe. converter. charactertostringconverter org.jbpm.context.exe. variableinstance. stringinstance
Java. Lang. Float org.jbpm.context.exe. converter. floattostringconverter org.jbpm.context.exe. variableinstance. stringinstance
Java. Lang. Double org.jbpm.context.exe. converter. doubletostringconverter org.jbpm.context.exe. variableinstance. stringinstance
Java. Io. serializable org.jbpm.context.exe. converter. serializabletostringconverter org.jbpm.context.exe. variableinstance. stringinstance

### Stored in a number-field in the database ###
Java. Lang. Long org.jbpm.context.exe. variableinstance. longinstance
Java. Lang. byte org.jbpm.context.exe. converter. bytetolongconverter org.jbpm.context.exe. variableinstance. longinstance
Java. Lang. Short org.jbpm.context.exe. converter. Convert tolongconverter org.jbpm.context.exe. variableinstance. longinstance
Java. Lang. Integer org.jbpm.context.exe. converter. integertolongconverter org.jbpm.context.exe. variableinstance. longinstance
Java. util. Date org.jbpm.context.exe. converter. datetolongconverter org.jbpm.context.exe. variableinstance. longinstance
The first column indicates the Java type, the third column indicates the type in the engine, and the middle column indicates the definition of the converter.

The concept of a converter is actually very simple. For example, if the Boolean value is true, it is a Java. Lang. boolean type in the program.
But in the jbpm3 database, it is a string "T" or "F", then a converter is required.
Org.jbpm.context.exe. converter. booleantostringconverter to convert.