In Camunda, expressions are a flexible way to calculate and manipulate data in process definitions and forms. Expressions can be used in various aspects of Camunda, such as service tasks, gateways, forms, conditions, etc.
Here are some common uses of Camunda expressions:
1. Calculated values: Expressions can be used to calculate values. For example, in a service task, you can use expressions to calculate results. In forms, expressions can be used to calculate displayed values.
2. Access process variables: expressions can be used to access the value of process variables. For example, in a service task, you can use expressions to read or write the value of a process variable. In forms, expressions can be used to display the values of process variables.
3. Judgment conditions: expressions can be used to judge conditions, for example, expressions are used in the gateway to determine the execution path of the next process step.
4. Calling functions: Expressions can be used to call functions defined in Java methods or other scripting languages.
Camunda supports many types of expressions, including simple expressions, EL expressions, script expressions, and Java expressions. You can choose the expression type that best suits your scenario according to your needs.
In summary, Camunda expressions are useful tools for manipulating data and computing results, and can be used in a variety of scenarios. Using expressions can make your process definitions more flexible and configurable, improving the maintainability and scalability of business processes.
How to use camunda expressions
In Camunda, you can use expressions in various aspects, including service tasks, gateways, forms and conditions, etc. Here are some common ways to use Camunda expressions:
1. Use simple expressions: You can use simple expressions in all aspects of Camunda. Simple expressions are simple string expressions such as: "${variableName}" or "${1 + 1}". You can use simple expressions to calculate values, access process variables, or perform conditional judgments. For example, in a service task, you can use the following expression to set the value of a process variable:
${execution.setVariable(“variableName”, “variableValue”)}
2. Use EL expressions: EL expressions are a standard Java expression language that can be used in Camunda's forms. Using EL expressions, you can access bean properties, call methods, or perform conditional judgments. For example, in Camunda's forms, you can use the following EL expression to display the value of a process variable:
${execution.getVariable("variableName")}
3. Use script expressions: script expressions refer to expressions written in script language. Camunda supports a variety of scripting languages, including JavaScript, Groovy, Python, Ruby, and more. You can use script expressions to calculate values, access process variables, or perform conditional judgments. For example, in a service task, you can use the following script expression to set the value of a process variable:
4. Use Java expressions: Java expressions refer to expressions written in the Java language. In Camunda's service tasks, you can use Java expressions to perform custom logic, such as computing results or accessing a database. For example, in Java code, you can use the following Java expression to set the value of a process variable:
execution.setVariable("variableName", "variableValue");
All in all, Camunda expressions are very flexible, and you can choose the expression type that best suits your scene according to your needs. Whether you use expressions in service tasks, gateways, forms, conditions, etc., you can easily process data and calculate results.