ExpressionEvaluationUtils (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

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org.springframework.web.util
Class ExpressionEvaluationUtils

java.lang.Object
  org.springframework.web.util.ExpressionEvaluationUtils

public abstract class ExpressionEvaluationUtils
extends Object
extends Object

Convenience methods for transparent access to JSP 2.0's built-in ExpressionEvaluator or the standalone ExpressionEvaluatorManager of Jakarta's JSTL implementation.

Automatically detects JSP 2.0 or Jakarta JSTL, preferring the JSP 2.0 mechanism if available. Also detects the JSP 2.0 API being present but the runtime JSP engine not actually supporting JSP 2.0, falling back to the Jakarta JSTL in this case. Throws an exception when encountering actual EL expressions if neither JSP 2.0 nor the Jakarta JSTL is available.

In the case of JSP 2.0, this class will by default use standard evaluate calls. If your application server happens to be inefficient in that respect, consider setting Spring's "cacheJspExpressions" context-param in web.xml to "true", which will use parseExpression calls with cached Expression objects instead.

The evaluation methods check if the value contains "${" before invoking the EL evaluator, treating the value as "normal" expression (i.e. a literal String value) else.

Note: The evaluation methods do not have a runtime dependency on JSP 2.0 or on Jakarta's JSTL implementation, as long as they are not asked to process actual EL expressions. This allows for using EL-aware tags with Java-based JSP expressions instead, for example.

Since:: 11.07.2003
Author:: Juergen Hoeller, Alef Arendsen
See Also:: ExpressionEvaluator.evaluate(java.lang.String, java.lang.Class, javax.servlet.jsp.el.VariableResolver, javax.servlet.jsp.el.FunctionMapper), ExpressionEvaluator.parseExpression(java.lang.String, java.lang.Class, javax.servlet.jsp.el.FunctionMapper), ExpressionEvaluatorManager

Field Summary

static String EXPRESSION_CACHE_CONTEXT_PARAM
          JSP 2.0 expression cache parameter at the servlet context level (i.e. a context-param in web.xml): "cacheJspExpressions".

static String EXPRESSION_PREFIX


static String EXPRESSION_SUFFIX


Constructor Summary

ExpressionEvaluationUtils()


Method Summary

static Object evaluate(String attrName, String attrValue, Class resultClass, PageContext pageContext)
          Evaluate the given expression (be it EL or a literal String value) to an Object of a given type,

static Object evaluate(String attrName, String attrValue, PageContext pageContext)
          Evaluate the given expression (be it EL or a literal String value) to an Object.

static boolean evaluateBoolean(String attrName, String attrValue, PageContext pageContext)
          Evaluate the given expression (be it EL or a literal String value) to a boolean.

static int evaluateInteger(String attrName, String attrValue, PageContext pageContext)
          Evaluate the given expression (be it EL or a literal String value) to an integer.

static String evaluateString(String attrName, String attrValue, PageContext pageContext)
          Evaluate the given expression (be it EL or a literal String value) to a String.

static boolean isExpressionLanguage(String value)
          Check if the given expression value is an EL expression.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Summary
`static String`	`EXPRESSION_CACHE_CONTEXT_PARAM` JSP 2.0 expression cache parameter at the servlet context level (i.e. a context-param in `web.xml`): "cacheJspExpressions".
`static String`	`EXPRESSION_PREFIX`
`static String`	`EXPRESSION_SUFFIX`

Constructor Summary
`ExpressionEvaluationUtils()`

Method Summary
`static Object`	`evaluate(String attrName, String attrValue, Class resultClass, PageContext pageContext)` Evaluate the given expression (be it EL or a literal String value) to an Object of a given type,
`static Object`	`evaluate(String attrName, String attrValue, PageContext pageContext)` Evaluate the given expression (be it EL or a literal String value) to an Object.
`static boolean`	`evaluateBoolean(String attrName, String attrValue, PageContext pageContext)` Evaluate the given expression (be it EL or a literal String value) to a boolean.
`static int`	`evaluateInteger(String attrName, String attrValue, PageContext pageContext)` Evaluate the given expression (be it EL or a literal String value) to an integer.
`static String`	`evaluateString(String attrName, String attrValue, PageContext pageContext)` Evaluate the given expression (be it EL or a literal String value) to a String.
`static boolean`	`isExpressionLanguage(String value)` Check if the given expression value is an EL expression.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

EXPRESSION_CACHE_CONTEXT_PARAM

public static final String EXPRESSION_CACHE_CONTEXT_PARAM

JSP 2.0 expression cache parameter at the servlet context level (i.e. a context-param in web.xml): "cacheJspExpressions".

See Also:: Constant Field Values

EXPRESSION_PREFIX

public static final String EXPRESSION_PREFIX

See Also:: Constant Field Values

EXPRESSION_SUFFIX

public static final String EXPRESSION_SUFFIX

See Also:: Constant Field Values

Constructor Detail