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Use Java string methods

You can use almost any Java string method to extract characters or manipulate expression strings.

Format​

The correct format for using a Java method with an expression is to wrap both the source expression and the method in the expression delimiter (<+...>), resulting in nested delimiters. For example:

<+<+expression>.methodName()>

The <+expression> calls the variable that you want to use the method on. Then you append the method and any parameters after the expression. The entire statement is wrapped in an expression delimiter (<+...>) so that Harness knows to evaluate the entire statement as one expression returning one, resolved value.

The content between the expression delimiter (<+...>) is passed to JEXL where it is evaluated. Using JEXL, you can build complex variable expressions that use JEXL methods. For example, here is an expression that uses Webhook Trigger payload information:

<+<+trigger.payload.pull_request.diff_url>.contains("triggerNgDemo")> || <+trigger.payload.repository.owner.name> == "harness-software"

Escaping​

If the method takes multiple, comma-separated arguments, and the method expects the parameters to be strings, you must wrap the expression in double quotes, except if it is a <+secrets.getValue()> expression.

Here is an example where an expression supplied as an argument for the replace() method. Because the parameter must be a string, the expression is wrapped in quotation marks.

<+<+pipeline.variables.var2>.replace("a", "<+pipeline.variables.var1>")>

Java string method examples​

Here are some examples of Java string methods with expressions.

contains()​

Use contains() to check if a value contains a certain string. Make sure to wrap the expression and the method within the expressions delimiter and wrap the target string in double quotes, such as <+<+EXPRESSION.TO.SEARCH>.contains("TARGET STRING")>.

For example, this expression uses contains() to check if a trigger payload field contains the string triggerDemo:

<+<+trigger.payload.pull_request.diff_url>.contains("triggerDemo")>

As another example, assume you have a variable deployEnv and you want to check if it contains the string prod. You can use contains() like this:

<+<+pipeline.variables.deployEnv>.contains("prod")>

You can also nest an expression in the contains() method to check if one expression contains the entire value of another expression, for example:

<+<+pipeline.variables.someVar>.contains(<+pipeline.variables.otherVar>)>

split()​

You might use split() if you want to extract certain details from a string or create an assertion expression based on a variable.

In this example, assume you have a pipeline variable called abc with value def:ghi. You might use split() like this:

<+pipeline.variables.abc.split(':')[1]>

This expression evaluates to ghi.

For this example, assume you have a pipeline variable called abc with value 5.6.0. You could use split() like this:

<+pipeline.variables.abc.split('\\.')[1]>

This expression resolves to 6.

To create an assertion expression from a variable, assume you have a variable someVar with the value prod-environment-variable. To extract prod from this value, you would use split() like this:

<+pipeline.variables.someVar.split('-')[0]>

charAt()​

Use charAt() to return the character at a specified index in a Harness variable expression string.

This can be useful, for example, with an expression such as <+artifact.tag> that contains a version number that you want to pull out.

To demonstrate this method, assume you have the expression <+version> with the value 1.2.3.

To get the first character of the string, you would use charAt() like this:

<+<+version>.charAt(0)>

This expression evaluates to 1.

substring()​

To demonstrate the substring() method, assume you have a variable someVar with the value prod-environment-variable. To extract prod from this value, you would use substring() like this:

<+<+pipeline.variables.someVar>.substring(0,3)>

Use multiple methods​

You can also use multiple, nested methods. For example, assume you have a variable called myvar with a value hello, and you use the methods substring and indexOf. You could use these methods like this:

<+<+stage.variables.myvar>.substring(<+<+stage.variables.myvar>.indexOf("e")>)>

This expression evaluates to ello.

Unsupported methods​

The getClass() method is not supported in expressions and it is not evaluated.