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SimpleEvaluationContext with dedicated factory methods for common cases

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Aligned with DataBindingPropertyAccessor and shown in ref doc examples.

Issue: SPR-16588
This commit is contained in:
Juergen Hoeller
2018-03-22 18:09:27 +01:00
parent 025ee83403
commit 51c57d77d9
8 changed files with 154 additions and 152 deletions
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93
src/docs/asciidoc/core/core-expressions.adoc
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@@ -186,9 +186,8 @@ out-of-the-box implementations.
* `SimpleEvaluationContext` -- exposes a subset of essential SpEL language features and
configuration options, for categories of expressions that do not require the full extent
of the SpEL language syntax and should be meaningfully restricted. Examples
include but are not limited to data binding expressions, property-based filters, and
others.
of the SpEL language syntax and should be meaningfully restricted. Examples include but
are not limited to data binding expressions, property-based filters, and others.
* `StandardEvaluationContext` -- exposes the full set of SpEL language features and
configuration options. You may use it to specify a default root object, and to configure
@@ -201,9 +200,9 @@ By default, the `create()` static factory method enables only read access to pro
You can also obtain a builder to configure the exact level of support needed, targeting
one of, or some combination of the following:
. Custom {@code PropertyAccessor} only (no reflection).
. Data binding properties for read-only access.
. Data binding properties for read and write.
. Custom {@code PropertyAccessor} only (no reflection)
. Data binding properties for read-only access
. Data binding properties for read and write
[[expressions-type-conversion]]
@@ -232,11 +231,10 @@ being placed in it. A simple example:
Simple simple = new Simple();
simple.booleanList.add(true);
SimpleEvaluationContext context = SimpleEvaluationContext().create();
EvaluationContext context = SimpleEvaluationContext().forReadOnlyDataBinding().build();
// false is passed in here as a string. SpEL and the conversion service will
// correctly recognize that it needs to be a Boolean and convert it
parser.parseExpression("booleanList[0]").setValue(context, simple, "false");
// b will be false
@@ -609,7 +607,7 @@ arrays and lists are obtained using square bracket notation.
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
SimpleEvaluationContext context = SimpleEvaluationContext.create();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
// Inventions Array
@@ -851,33 +849,33 @@ operators are demonstrated below.
[subs="verbatim,quotes"]
----
// Addition
int two = parser.parseExpression("1 + 1").getValue(Integer.class); // 2
int two = parser.parseExpression("1 + 1").getValue(Integer.class); // 2
String testString = parser.parseExpression(
"'test' + ' ' + 'string'").getValue(String.class); // 'test string'
"'test' + ' ' + 'string'").getValue(String.class); // 'test string'
// Subtraction
int four = parser.parseExpression("1 - -3").getValue(Integer.class); // 4
int four = parser.parseExpression("1 - -3").getValue(Integer.class); // 4
double d = parser.parseExpression("1000.00 - 1e4").getValue(Double.class); // -9000
double d = parser.parseExpression("1000.00 - 1e4").getValue(Double.class); // -9000
// Multiplication
int six = parser.parseExpression("-2 * -3").getValue(Integer.class); // 6
int six = parser.parseExpression("-2 * -3").getValue(Integer.class); // 6
double twentyFour = parser.parseExpression("2.0 * 3e0 * 4").getValue(Double.class); // 24.0
double twentyFour = parser.parseExpression("2.0 * 3e0 * 4").getValue(Double.class); // 24.0
// Division
int minusTwo = parser.parseExpression("6 / -3").getValue(Integer.class); // -2
int minusTwo = parser.parseExpression("6 / -3").getValue(Integer.class); // -2
double one = parser.parseExpression("8.0 / 4e0 / 2").getValue(Double.class); // 1.0
double one = parser.parseExpression("8.0 / 4e0 / 2").getValue(Double.class); // 1.0
// Modulus
int three = parser.parseExpression("7 % 4").getValue(Integer.class); // 3
int three = parser.parseExpression("7 % 4").getValue(Integer.class); // 3
int one = parser.parseExpression("8 / 5 % 2").getValue(Integer.class); // 1
int one = parser.parseExpression("8 / 5 % 2").getValue(Integer.class); // 1
// Operator precedence
int minusTwentyOne = parser.parseExpression("1+2-3*8").getValue(Integer.class); // -21
int minusTwentyOne = parser.parseExpression("1+2-3*8").getValue(Integer.class); // -21
----
@@ -892,14 +890,13 @@ done within a call to `setValue` but can also be done inside a call to `getValue
[subs="verbatim,quotes"]
----
Inventor inventor = new Inventor();
SimpleEvaluationContext context = SimpleEvaluationContext.create();
EvaluationContext context = SimpleEvaluationContext.forReadWriteDataBinding().build();
parser.parseExpression("Name").setValue(context, inventor, "Alexander Seovic2");
parser.parseExpression("Name").setValue(context, inventor, "Aleksandar Seovic");
// alternatively
String aleks = parser.parseExpression(
"Name = 'Alexandar Seovic'").getValue(context, inventor, String.class);
"Name = 'Aleksandar Seovic'").getValue(context, inventor, String.class);
----
@@ -960,12 +957,12 @@ are set using the method setVariable on `EvaluationContext` implementations.
[subs="verbatim,quotes"]
----
Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
SimpleEvaluationContext context = SimpleEvaluationContext.create();
EvaluationContext context = SimpleEvaluationContext.forReadWriteDataBinding().build();
context.setVariable("newName", "Mike Tesla");
parser.parseExpression("Name = #newName").getValue(context, tesla);
System.out.println(tesla.getName()) // "Mike Tesla"
System.out.println(tesla.getName()) // "Mike Tesla"
----
@@ -986,8 +983,8 @@ an expression are evaluated, #root always refers to the root.
// create parser and set variable 'primes' as the array of integers
ExpressionParser parser = new SpelExpressionParser();
SimpleEvaluationContext context = SimpleEvaluationContext.create();
context.setVariable("primes",primes);
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataAccess();
context.setVariable("primes", primes);
// all prime numbers > 10 from the list (using selection ?{...})
// evaluates to [11, 13, 17]
@@ -1008,7 +1005,7 @@ expression string. The function is registered through the `EvaluationContext`.
----
Method method = ...;
SimpleEvaluationContext context = SimpleEvaluationContext.create();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
context.setVariable("myFunction", method);
----
@@ -1020,7 +1017,7 @@ For example, given a utility method to reverse a string is shown below:
public abstract class StringUtils {
public static String reverseString(String input) {
StringBuilder backwards = new StringBuilder();
StringBuilder backwards = new StringBuilder(input.length());
for (int i = 0; i < input.length(); i++)
backwards.append(input.charAt(input.length() - 1 - i));
}
@@ -1035,13 +1032,13 @@ The above method can then be registered and used as follows:
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
SimpleEvaluationContext context = SimpleEvaluationContext.create();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
context.setVariable("reverseString",
StringUtils.class.getDeclaredMethod("reverseString", String.class));
StringUtils.class.getDeclaredMethod("reverseString", String.class));
String helloWorldReversed = parser.parseExpression(
"#reverseString('hello')").getValue(context, String.class);
"#reverseString('hello')").getValue(context, String.class);
----
@@ -1056,7 +1053,7 @@ lookup beans from an expression using the (@) symbol.
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
StandardEvaluationContext context = StandardEvaluationContext.create();
StandardEvaluationContext context = new StandardEvaluationContext();
context.setBeanResolver(new MyBeanResolver());
// This will end up calling resolve(context,"foo") on MyBeanResolver during evaluation
@@ -1069,7 +1066,7 @@ To access a factory bean itself, the bean name should instead be prefixed with a
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
StandardEvaluationContext context = StandardEvaluationContext.create();
StandardEvaluationContext context = new StandardEvaluationContext();
context.setBeanResolver(new MyBeanResolver());
// This will end up calling resolve(context,"&foo") on MyBeanResolver during evaluation
@@ -1124,7 +1121,7 @@ example:
[subs="verbatim,quotes"]
----
String name = "Elvis Presley";
String displayName = name != null ? name : "Unknown";
String displayName = (name != null ? name : "Unknown");
----
Instead you can use the Elvis operator, named for the resemblance to Elvis' hair style.
@@ -1135,8 +1132,7 @@ Instead you can use the Elvis operator, named for the resemblance to Elvis' hair
ExpressionParser parser = new SpelExpressionParser();
String name = parser.parseExpression("name?:'Unknown'").getValue(String.class);
System.out.println(name); // 'Unknown'
System.out.println(name); // 'Unknown'
----
Here is a more complex example.
@@ -1145,19 +1141,15 @@ Here is a more complex example.
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
SimpleEvaluationContext context = SimpleEvaluationContext.create();
String name = parser.parseExpression("Name?:'Elvis Presley'").getValue(context, tesla, String.class);
System.out.println(name); // Nikola Tesla
System.out.println(name); // Nikola Tesla
tesla.setName(null);
name = parser.parseExpression("Name?:'Elvis Presley'").getValue(context, tesla, String.class);
System.out.println(name); // Elvis Presley
System.out.println(name); // Elvis Presley
----
@@ -1175,20 +1167,17 @@ safe navigation operator will simply return null instead of throwing an exceptio
[subs="verbatim,quotes"]
----
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
tesla.setPlaceOfBirth(new PlaceOfBirth("Smiljan"));
SimpleEvaluationContext context = SimpleEvaluationContext.create();
String city = parser.parseExpression("PlaceOfBirth?.City").getValue(context, tesla, String.class);
System.out.println(city); // Smiljan
System.out.println(city); // Smiljan
tesla.setPlaceOfBirth(null);
city = parser.parseExpression("PlaceOfBirth?.City").getValue(context, tesla, String.class);
System.out.println(city); // null - does not throw NullPointerException!!!
System.out.println(city); // null - does not throw NullPointerException!!!
----
[NOTE]