SpEL documentation refinements (backported from 5.1.x)

Author: jhoeller

src/docs/asciidoc/core/core-expressions.adoc

@@ -119,11 +119,12 @@ as shown below.
 	byte[] bytes = (byte[]) exp.getValue();
 ----
 
-SpEL also supports nested properties using the standard _dot_ notation, i.e.
-`prop1.prop2.prop3` and also the corresponding setting of property values.
-
+SpEL also supports nested properties by using the standard dot notation (such as
+`prop1.prop2.prop3`) and also the corresponding setting of property values.
 Public fields may also be accessed.
 
+The following example shows how to use dot notation to get the length of a literal:
+
 [source,java,indent=0]
 [subs="verbatim,quotes"]
 ----
@@ -287,22 +288,21 @@ It is also possible to configure the behaviour of the SpEL expression compiler.
 === SpEL compilation
 
 Spring Framework 4.1 includes a basic expression compiler. Expressions are usually
-interpreted which provides a lot of dynamic flexibility during evaluation but
-does not provide optimum performance. For occasional expression usage
-this is fine, but when used by other components like Spring Integration, 
-performance can be very important and there is no real need for the dynamism.
-
-The SpEL compiler is intended to address this need. The  compiler will generate a
-real Java class on the fly during evaluation that embodies the expression behavior
-and use that to achieve much faster expression evaluation. Due to the lack of
-typing around expressions the compiler uses information gathered during the
-interpreted evaluations of an expression when performing compilation. For example,
-it does not know the type of a property reference purely from the expression but
-during the first interpreted evaluation it will find out what it is. Of course,
-basing the compilation on this information could cause trouble later if the types
-of the various expression elements change over time. For this reason compilation
-is best suited to expressions whose type information is not going to change on
-repeated evaluations.
+interpreted, which provides a lot of dynamic flexibility during evaluation but
+does not provide optimum performance. For occasional expression usage,
+this is fine, but, when used by other components such as Spring Integration,
+performance can be very important, and there is no real need for the dynamism.
+
+The SpEL compiler is intended to address this need. During evaluation, the compiler
+generates a Java class that embodies the expression behavior at runtime and uses that
+class to achieve much faster expression evaluation. Due to the lack of typing around
+expressions, the compiler uses information gathered during the interpreted evaluations
+of an expression when performing compilation. For example, it does not know the type
+of a property reference purely from the expression, but during the first interpreted
+evaluation, it finds out what it is. Of course, basing compilation on such derived
+information can cause trouble later if the types of the various expression elements
+change over time. For this reason, compilation is best suited to expressions whose
+type information is not going to change on repeated evaluations.
 
 For a basic expression like this:
 
@@ -360,24 +360,24 @@ After selecting a mode, use the `SpelParserConfiguration` to configure the parse
 	Object payload = expr.getValue(message);
 ----
 
-When specifying the compiler mode it is also possible to specify a classloader (passing null is allowed).
-Compiled expressions will be defined in a child classloader created under any that is supplied.
-It is important to ensure if a classloader is specified it can see all the types involved in
-the expression evaluation process. If none is specified then a default classloader will be used
+When you specify the compiler mode, you can also specify a classloader (passing null is allowed).
+Compiled expressions are defined in a child classloader created under any that is supplied.
+It is important to ensure that, if a classloader is specified, it can see all the types involved in
+the expression evaluation process. If you do not specify a classloader, a default classloader is used
 (typically the context classloader for the thread that is running during expression evaluation).
 
 The second way to configure the compiler is for use when SpEL is embedded inside some other
-component and it may not be possible to configure via a configuration object. In these cases
-it is possible to use a system property. The property `spring.expression.compiler.mode` can be
-set to one of the `SpelCompilerMode`  enum values (`off`, `immediate`, or `mixed`).
+component and it may not be possible to configure it through a configuration object. In these
+cases, it is possible to use a system property. You can set the `spring.expression.compiler.mode`
+property to one of the `SpelCompilerMode` enum values (`off`, `immediate`, or `mixed`).
 
 
 [[expressions-compiler-limitations]]
 ==== Compiler limitations
 
-Since Spring Framework 4.1 the basic compilation framework is in place. However, the framework
+Since Spring Framework 4.1, the basic compilation framework is in place. However, the framework
 does not yet support compiling every kind of expression. The initial focus has been on the
-common expressions that are likely to be used in performance critical contexts. The following
+common expressions that are likely to be used in performance-critical contexts. The following
 kinds of expression cannot be compiled at the moment:
 
 - expressions involving assignment