Spring 表达式语言 (SpEL)

相关源文件

• framework-docs/modules/ROOT/pages/core/expressions.adoc
• framework-docs/modules/ROOT/pages/core/expressions/evaluation.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/array-construction.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/collection-projection.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/collection-selection.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/constructors.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/functions.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/methods.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/operator-elvis.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/operator-safe-navigation.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/operators.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/properties-arrays.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/templating.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/varargs.adoc
• framework-docs/modules/ROOT/pages/core/expressions/language-ref/variables.adoc
• spring-context/src/test/resources/org/springframework/jmx/export/notificationPublisherTests.xml
• spring-core/src/main/java/org/springframework/core/convert/Property.java
• spring-expression/spring-expression.gradle
• spring-expression/src/main/java/org/springframework/expression/EvaluationContext.java
• spring-expression/src/main/java/org/springframework/expression/TypedValue.java
• spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java
• spring-expression/src/main/java/org/springframework/expression/spel/CompilablePropertyAccessor.java
• spring-expression/src/main/java/org/springframework/expression/spel/SpelCompilerMode.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Assign.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/CompoundExpression.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/ConstructorReference.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Elvis.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/FunctionReference.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/MethodReference.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/OpDec.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/OpInc.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/OperatorBetween.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/OperatorInstanceof.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Projection.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/PropertyOrFieldReference.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Selection.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/SpelNodeImpl.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/Ternary.java
• spring-expression/src/main/java/org/springframework/expression/spel/ast/VariableReference.java
• spring-expression/src/main/java/org/springframework/expression/spel/standard/InternalSpelExpressionParser.java
• spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/DataBindingMethodResolver.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/DataBindingPropertyAccessor.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectionHelper.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveConstructorExecutor.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveConstructorResolver.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodExecutor.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodResolver.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectivePropertyAccessor.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/SimpleEvaluationContext.java
• spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java
• spring-expression/src/test/java/example/Color.java
• spring-expression/src/test/java/org/springframework/expression/spel/AbstractExpressionTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/ArrayConstructorTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/BooleanExpressionTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/CachedMethodExecutorTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/EvaluationTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/IndexingTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/MethodInvocationTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/OptionalNullSafetyTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/ParsingTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/PropertyAccessTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/SpelDocumentationTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/SpelReproTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/TestScenarioCreator.java
• spring-expression/src/test/java/org/springframework/expression/spel/VariableAndFunctionTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/support/ReflectionHelperTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/support/SimpleEvaluationContextTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/support/StandardComponentsTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/support/StandardEvaluationContextTests.java
• spring-expression/src/test/java/org/springframework/expression/spel/testresources/Inventor.java
• spring-expression/src/test/kotlin/org/springframework/expression/spel/SpelReproKotlinTests.kt

Spring表达式语言（SpEL）是一种强大的表达式语言，支持在运行时查询和操作对象图。它在Spring框架内提供了一个统一的表达式求值框架，能够进行动态属性访问、方法调用、集合操作以及带有可选字节码编译的复杂表达式求值以优化性能。

有关核心实用工具和类型转换的信息，请参阅核心实用工具和类型系统与转换。有关注解处理功能，请参阅注解处理。

架构概述

SpEL遵循传统的解释器模式，并具有可选的编译功能。该系统通过标记化、解析和AST构造将文本表达式转换为可执行代码。

高级表达式处理流程

来源： spring-expression/src/main/java/org/springframework/expression/spel/standard/InternalSpelExpressionParser.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/standard/SpelCompiler.java1-50

核心系统组件

来源： spring-expression/src/main/java/org/springframework/expression/spel/standard/SpelExpressionParser.java1-100 spring-expression/src/main/java/org/springframework/expression/spel/ast/SpelNodeImpl.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java1-100

解析和AST构建

解析系统将表达式字符串转换为可执行的抽象语法树（AST）。每个AST节点都实现了SpelNodeImpl，并提供了解释和可选的编译功能。

关键AST节点类型

节点类型	目的	示例表达式
Indexer	数组、列表、映射和对象索引	array[0], map['key'], obj['property']
MethodReference	方法调用	object.method(args)
PropertyOrFieldReference	属性/字段访问	object.property
FunctionReference	函数调用	#functionName(args)
ConstructorReference	对象构造	new java.lang.String('text')

Indexer实现细节

Indexer类为各种数据结构提供了全面的索引功能。

Indexer使用?.[]运算符支持空安全操作，并通过配置的TypeConverter进行类型自动转换。

来源： spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java48-87 spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java501-1067

评估系统

求值系统在EvaluationContext中执行AST节点，该上下文提供变量、函数、类型转换器以及属性/方法解析器的访问权限。

求值上下文层级

表达式状态和值引用

在求值期间，AST节点使用ExpressionState来维护上下文，并使用ValueRef实现来进行读/写操作。

来源： spring-expression/src/main/java/org/springframework/expression/spel/ExpressionState.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/ast/SpelNodeImpl.java200-250

属性和方法访问

SpEL通过可配置的访问器接口提供灵活的属性和方法访问，默认实现支持基于反射的访问。

属性访问系统

ReflectivePropertyAccessor是属性访问的主要实现，支持基于字段和方法的属性访问。

方法解析

ReflectiveMethodResolver处理方法发现和调用，支持可变参数、类型转换和方法缓存。

方法解析功能	实现
方法重载	ArgumentsMatchKind评分系统
可变参数支持	ReflectionHelper.convertAllArguments()
类型转换	通过TypeConverter自动进行
缓存	CachedMethodExecutor用于性能优化

来源： spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectivePropertyAccessor.java72-115 spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodResolver.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectionHelper.java49-135

索引和自定义访问器

SpEL的索引系统不仅限于基本的数组/集合访问，还通过IndexAccessor接口支持自定义数据结构。

内置索引支持

自定义IndexAccessor实现

ReflectiveIndexAccessor通过委托给指定的getter/setter方法来实现对自定义类型的索引。

来源： spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java217-304 spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveIndexAccessor.java1-50

编译系统

SpEL包含一个复杂的编译系统，可以将解释过的AST节点转换为高效的字节码，以满足性能关键型场景的需求。

编译架构

节点类型的编译支持

AST节点类型	编译支持	要求
Indexer	完全支持	公共类型，兼容的访问器
MethodReference	完全支持	公共方法，无参数转换
PropertyOrFieldReference	完全支持	公共属性/字段
FunctionReference	部分支持	仅限静态方法
ConstructorReference	完全支持	公共构造函数

CodeFlow管理

CodeFlow类负责管理字节码生成状态，包括类型描述符、变量分配和指令生成。

来源： spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java47-106 spring-expression/src/main/java/org/springframework/expression/spel/standard/SpelCompiler.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java307-336

关键扩展点

SpEL提供了几个关键接口，支持自定义和扩展表达式求值能力。

主要扩展接口

接口	目的	关键方法
PropertyAccessor	自定义属性访问	canRead(), read(), canWrite(), write()
MethodResolver	自定义方法解析	resolve()
IndexAccessor	自定义索引支持	canRead(), read(), canWrite(), write()
TypeConverter	类型转换	canConvert(), convertValue()
BeanResolver	Bean引用解析	resolve()

支持编译的扩展

对于性能关键型场景，扩展接口可以实现支持编译的变体。

来源： spring-expression/src/main/java/org/springframework/expression/spel/CompilablePropertyAccessor.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/CompilableIndexAccessor.java1-50 spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java100-200