[Spring Framework Core] 4.3. Language Reference (1)

https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#expressions-language-ref

Core Technologies

 

잘못된 내용이 있다면 알려주세요 감사합니다 😌

 

---

 

Spring Expression Language 스프링 표현식 언어(SpEL)

https://spring.io/tools

Spring | Home

 

공식문서로 한번 읽어주면 좋을 것 같은 표현식 레퍼런스를 정리해본다

 

This section describes how the Spring Expression Language works. It covers the following topics:

 

• Literal Expressions
• Properties, Arrays, Lists, Maps, and Indexers
• Inline Lists
• Inline Maps
• Array Construction
• Methods
• Operators
• Types
• Constructors
• Variables
• Functions
• Bean References
• Ternary Operator (If-Then-Else)
• The Elvis Operator
• Safe Navigation Operator

 

4.3.1. Literal Expressions ~ 4.3.6. Methods

 

 

 

4.3.1. Literal Expressions

SpEL supports the following types of literal expressions.

• strings
• numeric values: integer (int or long), hexadecimal (int or long), real (float or double)
• boolean values: true or false
• null

문자열, 숫자 값(정수, 16진수, 실수), bool, null

 

 

ExpressionParser parser = new SpelExpressionParser();

// evaluates to "Hello World"
String helloWorld = (String) parser.parseExpression("'Hello World'").getValue();

// evaluates to "Tony's Pizza"
String pizzaParlor = (String) parser.parseExpression("'Tony''s Pizza'").getValue();

double avogadrosNumber = (Double) parser.parseExpression("6.0221415E+23").getValue();

// evaluates to 2147483647
int maxValue = (Integer) parser.parseExpression("0x7FFFFFFF").getValue();

boolean trueValue = (Boolean) parser.parseExpression("true").getValue();

Object nullValue = parser.parseExpression("null").getValue();

 

 

 

4.3.2. Properties, Arrays, Lists, Maps, and Indexers

Property를 사용하면 탐색하기기 쉽다

 

이건 사용할 예제

https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#expressions-example-classes

Core Technologies

public class Inventor {

    private String name;
    private String nationality;
    private String[] inventions;
    private Date birthdate;
    private PlaceOfBirth placeOfBirth;

    public Inventor(String name, String nationality) {
        GregorianCalendar c= new GregorianCalendar();
        this.name = name;
        this.nationality = nationality;
        this.birthdate = c.getTime();
    }

    public Inventor(String name, Date birthdate, String nationality) {
        this.name = name;
        this.nationality = nationality;
        this.birthdate = birthdate;
    }

    public Inventor() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getNationality() {
        return nationality;
    }

    public void setNationality(String nationality) {
        this.nationality = nationality;
    }

    public Date getBirthdate() {
        return birthdate;
    }

    public void setBirthdate(Date birthdate) {
        this.birthdate = birthdate;
    }

    public PlaceOfBirth getPlaceOfBirth() {
        return placeOfBirth;
    }

    public void setPlaceOfBirth(PlaceOfBirth placeOfBirth) {
        this.placeOfBirth = placeOfBirth;
    }

    public void setInventions(String[] inventions) {
        this.inventions = inventions;
    }

    public String[] getInventions() {
        return inventions;
    }
}

public class PlaceOfBirth {

    private String city;
    private String country;

    public PlaceOfBirth(String city) {
        this.city=city;
    }

    public PlaceOfBirth(String city, String country) {
        this(city);
        this.country = country;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String s) {
        this.city = s;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }
}

public class Society {

    private String name;

    public static String Advisors = "advisors";
    public static String President = "president";

    private List<Inventor> members = new ArrayList<Inventor>();
    private Map officers = new HashMap();

    public List getMembers() {
        return members;
    }

    public Map getOfficers() {
        return officers;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public boolean isMember(String name) {
        for (Inventor inventor : members) {
            if (inventor.getName().equals(name)) {
                return true;
            }
        }
        return false;
    }
}

 

 

출생연도와 출생도시 탐색하기

// evaluates to 1856
int year = (Integer) parser.parseExpression("birthdate.year + 1900").getValue(context);

String city = (String) parser.parseExpression("placeOfBirth.city").getValue(context);

 

 contents of arrays and lists are obtained - array, list에서는 대괄호 표기법 사용

ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();

// Inventions Array

// evaluates to "Induction motor"
String invention = parser.parseExpression("inventions[3]").getValue(
        context, tesla, String.class);

// Members List

// evaluates to "Nikola Tesla"
String name = parser.parseExpression("members[0].name").getValue(
        context, ieee, String.class);

// List and Array navigation
// evaluates to "Wireless communication"
String invention = parser.parseExpression("members[0].inventions[6]").getValue(
        context, ieee, String.class);

 

Map 에서는 키값을 지정해서 가져옴

// Officer's Dictionary

Inventor pupin = parser.parseExpression("officers['president']").getValue(
        societyContext, Inventor.class);

// evaluates to "Idvor"
String city = parser.parseExpression("officers['president'].placeOfBirth.city").getValue(
        societyContext, String.class);

// setting values
parser.parseExpression("officers['advisors'][0].placeOfBirth.country").setValue(
        societyContext, "Croatia");

 

 

 

 

4.3.3. Inline Lists

// evaluates to a Java list containing the four numbers
List numbers = (List) parser.parseExpression("{1,2,3,4}").getValue(context);

List listOfLists = (List) parser.parseExpression("{{'a','b'},{'x','y'}}").getValue(context);

 

 

{} by itself means an empty list.

{} 이것 자체가 비어있다는 의미

 

For performance reasons, if the list is itself entirely composed of fixed literals, a constant list is created to represent the expression (rather than building a new list on each evaluation).

 

 

4.3.4. Inline Maps

 

You can also directly express maps in an expression by using {key:value} notation. The following example shows how to do so:

// evaluates to a Java map containing the two entries
Map inventorInfo = (Map) parser.parseExpression("{name:'Nikola',dob:'10-July-1856'}").getValue(context);

Map mapOfMaps = (Map) parser.parseExpression("{name:{first:'Nikola',last:'Tesla'},dob:{day:10,month:'July',year:1856}}").getValue(context);

 

{:} by itself means an empty map.

위와 같음 {:} 근데 이렇게 써본 적 없는 듯...

For performance reasons, if the map is itself composed of fixed literals or other nested constant structures (lists or maps), a constant map is created to represent the expression (rather than building a new map on each evaluation). Quoting of the map keys is optional (unless the key contains a period (.)). The examples above do not use quoted keys.

 

 

4.3.5. Array Construction

You can build arrays by using the familiar Java syntax, optionally supplying an initializer to have the array populated at construction time. The following example shows how to do so:

int[] numbers1 = (int[]) parser.parseExpression("new int[4]").getValue(context);

// Array with initializer
int[] numbers2 = (int[]) parser.parseExpression("new int[]{1,2,3}").getValue(context);

// Multi dimensional array
int[][] numbers3 = (int[][]) parser.parseExpression("new int[4][5]").getValue(context);

 

You cannot currently supply an initializer when you construct a multi-dimensional array.

 

 

4.3.6. Methods

You can invoke methods by using typical Java programming syntax. You can also invoke methods on literals. Variable arguments are also supported. The following examples show how to invoke methods:

// string literal, evaluates to "bc"
String bc = parser.parseExpression("'abc'.substring(1, 3)").getValue(String.class);

// evaluates to true
boolean isMember = parser.parseExpression("isMember('Mihajlo Pupin')").getValue(
        societyContext, Boolean.class);