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对于最新的稳定版本，请使用 Spring Framework 6.2.0！ |
功能
您可以通过注册可在
expression 字符串。该函数通过EvaluationContext.这
以下示例演示如何注册用户定义的函数：
-
Java
-
Kotlin
Method method = ...;
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
context.setVariable("myFunction", method);val method: Method = ...
val context = SimpleEvaluationContext.forReadOnlyDataBinding().build()
context.setVariable("myFunction", method)例如，请考虑以下反转字符串的实用程序方法：
-
Java
-
Kotlin
public abstract class StringUtils {
public static String reverseString(String input) {
StringBuilder backwards = new StringBuilder(input.length());
for (int i = 0; i < input.length(); i++) {
backwards.append(input.charAt(input.length() - 1 - i));
}
return backwards.toString();
}
}fun reverseString(input: String): String {
val backwards = StringBuilder(input.length)
for (i in 0 until input.length) {
backwards.append(input[input.length - 1 - i])
}
return backwards.toString()
}然后，您可以注册并使用上述方法，如下例所示：
-
Java
-
Kotlin
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
context.setVariable("reverseString",
StringUtils.class.getDeclaredMethod("reverseString", String.class));
String helloWorldReversed = parser.parseExpression(
"#reverseString('hello')").getValue(context, String.class);val parser = SpelExpressionParser()
val context = SimpleEvaluationContext.forReadOnlyDataBinding().build()
context.setVariable("reverseString", ::reverseString::javaMethod)
val helloWorldReversed = parser.parseExpression(
"#reverseString('hello')").getValue(context, String::class.java)