Available Features

Overview

Feature is an interface which provide ability to store and query additional information based on bytecode. Feature can be installed only when instance of JCDB is created.

    val db = jcdb {
        useProcessJRE()
        persistent("/tmp/compilation-db/${System.currentTimeMillis()}") // persist data
        installFeatures(Usages, InMemoryHierarchy)
    }

InMemoryHierarchy feature

By default JCDB stores information about class hierarchy in sql database (table ClassHierarchies with columns: class_id, super_id, is_interface). This brings ability to retrieve whole hierarchy for particular class with recursive sql query. Recursive queries are quite common and quite slow.

InMemoryHierarchy - solves performance problem op built-in solution. It's introduce in-memory cache which fast searching.

Overhead for memory is O(number of classes). For own project with about 50K classes (including runtime) memory consumption for such cache is ~6,5Mb of heap memory.

Usages feature

Brings ability to find out places where methods and fields are used.

It's recommended to install InMemoryHierarchy for performance purposes

    val db = jcdb {
        useProcessJRE()
        load(allClasspath)
        persistent("/tmp/compilation-db/${System.currentTimeMillis()}") // persist data
        installFeatures(Usages, InMemoryHierarchy)
    }
    val method = run // java.lang.Runnable#run method
    val field = field // java.lang.String#value field

    val cp = db.classpath(allClasspath)
    cp.findUsages(method) // sequence of methods which calls `method`
    cp.findUsages(field, FieldUsageMode.READ) // sequence of fields which reads `field` value

Usages indexer goes through all instructions and collect method calls or fields access and store it into table:

Column name	Column description
callee_class_symbol_id	callee class name unique identifier
callee_name_symbol_id	method/field name unique identifier
callee_desc_hash	null for field usage. Sip hash of method bytecode description for methods
opcode	instruction operation code
caller_class_symbols_id	caller class name unique identifier
caller_method_offsets	method numbers for this usage
location_id	location identifier