What is a BML file?
A BML file, identified by the .bml extension, is a configuration file written in the Bean Markup Language. Originally developed by IBM alphaWorks, this XML-based language was created to describe the structures and relationships between components within a Java application. Its primary function is to declaratively specify how different software components, or “beans,” are connected and wired together to perform complex tasks. This approach provides a significant advantage: it allows developers to access and configure Java objects and their methods without the need to write new foundational Java classes from scratch. By externalizing this configuration, BML promotes modularity and simplifies application setup. For viewing or editing, these files are stored in plain text format and can be opened with any common text editor, including Microsoft Notepad, Notepad++, or even standard web browsers.
BML File Format
The IBM alphaworks website has provided two implementations of BML. The First implementation is an interpreter that ‘plays’ a BML script for generating the desired bean hierarchy. The second implementation is a compiler that compiles any BML script into reflection-free Java code. This is advantageous in the sense that it allows capturing the inter-component structure of the application using a language that is designed for this specific purpose with the added ability to compile it into ‘regular’ Java code.
BML Tags
The following is an explanation of some of the tags used in the BML language:
The tag:
The element is used to create new beans or to look up beans by name. The tag is of the format:
<bean class = "classname or serialized file" [id = "name"]>
</bean>
The “id” in the tag is associated with the object registry for the JavaBean.
The tag
There are two ways the string tag can be used:
- To create a non-empty string:
<string [value = "value of string"]> [value of string]
</string>
- To create an empty string:
<string/>
Key Characteristics of the BML File Format
| Characteristic | Description |
|---|---|
| File Extension | .bml |
| Declarative Programming | Shifts object assembly from imperative Java code to declarative XML configuration. |
| Framework-Specific | Primarily associated with the Apache Jakarta Commons BeanUtils library and early versions of the Spring Framework (pre-annotation and JavaConfig). |
| Precursor to Modern DI | Direct historical ancestor of the configuration styles used in Spring XML files (applicationContext.xml). |
| Verbose Syntax | As an XML format, BML can be more verbose compared to modern alternatives like Java annotations or YAML. |
| Reduced Usage | Largely superseded by annotation-driven configuration (e.g., @Autowired, @Component) in contemporary Java development. |
| Niche Legacy Role | Still encountered in maintaining and modernizing legacy enterprise Java applications. |
FAQ
Q1: What program opens a BML file?
A: BML files are plain text XML files and can be opened with any text editor (Notepad++, VS Code) or XML editor, but they are processed by specific Java libraries like Apache Commons BeanUtils.
Q2: Are BML files still used today?
A: Their use is minimal in new projects, but they are critical for maintaining and understanding legacy Java systems built in the early-to-mid 2000s.
Q3: What is the difference between BML and Spring XML?
A: BML was a foundational concept; Spring Framework’s XML configuration is a more powerful, feature-rich evolution of the same core idea for dependency injection.
Q4: Can a BML file run by itself?
A: No, a BML file is a passive configuration file; it requires a Java runtime and a specific BML processor library to interpret and execute its instructions.
Q5: Is BML related to other “BML” formats like Blissymbolics?
A: No, this is a namespace collision. In other contexts, BML can mean Blissymbolics Markup Language (for communication) or Behavior Markup Language (for animations), which are entirely unrelated to Java.
