This chapter describes the RL command-line that reads rulesets from System.in and writes output from the functions println, watch, and, show to System.out.
The chapter includes the following topics:
The following invocation provides a simple command-line interface, with the prompt, RL>.
Example without Java Beans:
java -jar SOA_ORACLE_HOME/soa/modules/oracle.rules_11.1.1/rl.jar -p "RL> "
Where SOA_ORACLE_HOME is where SOA modules are installed (for example, c:/Oracle/Middleware). The –p option specifies the prompt.
The following shows how an RL Language command-line can be started that can access this Java bean:
java -classpath SOA_ORACLE_HOME/soa/modules/oracle.rules_11.1.1/rl.jar;BeanPath oracle.rules.rl.session.CommandLine -p "RL> "
Where BeanPath is the classpath component to any supplied Java Bean classes.
To exit the command-line interface, use the special action exit; at the command prompt. The exit; action cannot be in an included ruleset. Alternatively, to exit you can invoke the System.exit(int) method in any action.
The RL command-line interface accumulates input line by line, and interprets the input when the input stream includes either:
A complete named ruleset
One or more complete import, include, ruleset, definition, action commands within an unnamed ruleset.
Note:
The if,else and try, catch, and finally actions require lookahead to determine where they end. In order to execute an if without an else clause, or a try without a finally clause at the RL command-line, you should add a semicolon terminator.
This is not necessary if you execute RL using include, or using the RuleSession API.
The following code example shows a sample RL command-line input processing:
RL> int i = 1;
RL> if (i > 0) {println("i positive");}
// nothing happens - waiting for possible "else"
;
i positive
RL>
Input must be complete at the end of a line. For example, if an action ends in the middle of a line, then that action is not interpreted until some following action is complete at the end of a line.
Example 4-1 Sample Command-Line Input Processing - Waiting for End of Line
RL> println("delayed"
); println("hello"
); println("world");
delayed
hello
world
RL>
Notes for using command-line input processing:
The command-line segments its input into blocks and then feeds each block to the interpreter. If you never type a closing brace or semicolon, no error is raised because the command line waits for input before it does a full parse of the block
The command-line interpreter, when used interactively or with the –i option, collapses the input, for line numbering purposes, into "small" rulesets ending at a newline. Errors are reported with numbers within the ruleset.
For example, if the input consists of the following:
int i = 0; i = 1; // this is a ruleset i = "i"; // this is another ruleset
For this example, command-line reports an error as follows:
Oracle Business Rules RL: type check error ConversionException: cannot convert from type 'java.lang.String' to type 'int' at line 1 column 5 in main
To avoid this behavior, you can explicitly enclose the input in a ruleset. For example,
ruleset main {
int i = 0; i = 1;
i = "i";
}
Now, the error is on line 3 or, you can include the input file using an include.
The following table provides a description of the RL command line options.
Table 4-1 RL Command-Line Options
| Flag | Description |
|---|---|
|
–i |
Read rulesets from the file named by the next argument, instead of from the default, For example, -i myInput.rl Note: the command-line segments its input into blocks and then feeds each block to the interpreter. If the file |
|
–c |
Executes the next argument as the first RL command, then start reading input. This option is useful to include a file of settings and functions for debugging. For example, -c "include file:debugSettings.rl;" If you do not want to read from the input after executing the command, include "exit;" after the command. For example, -c "include file:script.rl; exit;" |
|
–p |
Sets the next argument as the prompt string. For example, -p "RL> " |
|
-o |
Specifies where to write output from For example: –o debug.log |
|
–v |
Print version information. |
This section lists commands that are implemented by the RL command-line interface (these commands are not part of RL).
Thus, these commands cannot appear in blocks or be included rulesets.
Discard the current RuleSession object and allocate a new one. The effect is that all rules, variables, classes, and functions are discarded.
Instead of using clear; to restart a command-line you can also type exit; and then reissue the Java command to start another command-line.