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Lenguaje de script JavaPath para acceder a estructuras de datos complejas

El artículo analiza el lenguaje de scripting declarativo JavaPath como una alternativa al uso de Java Reflection y una forma de evitar el "infierno del servicio" en aplicaciones independientes que usan estructuras de datos complejas.


Descripción del problema


Considere una estructura profundamente anidada


class A{
   B b;
}
class B{
   C c;
}
class C{
   String name;
}

Si necesitamos asignar un valor al campo de nombre de la clase C sin tener acceso directo a la instancia A, entonces una capa intermedia de la API del servicio viene al rescate.


private A a;
public void setNameService(String name) {
    a.b.c.name = name;
}

, , . , .


private A a;
public void setNameService(String name) {
    if(a == null) {
        a = new A();
    }
    if(a.b == null) {
        a.b = new B();
    }
    if(a.b.c == null) {
        a.b.c = new C();
    }
    a.b.c.name = name;
}

, , setNameService(String name) , , a, b c, , .


API, , , API. . , . , , 'C' name, 'B' 'A' .


, - . , , , . - - . , . , , , , .


JavaPath , .


JavaPath


JavaPath.


private A a = new A();
private final JavaPath javaPath = new JavaPath(A.class);

public void setNameService(String name) {
    javaPath.evalPath("b.c.name", a, name);
}

setNameService.


, JavaPath — , Java. JavaPath . , . JavaPath . -public. . JavaPath private final .


: — JavaPath!


final String str = "VALUE";
JavaPath javaPath = new JavaPath(String.class);
assertEquals("VALUE",str);
//  private final byte[] value;  String 
javaPath.evalPath("value",str,"THE HACK".getBytes());
assertEquals("THE HACK",str);

- , , JavaPath Java Reflection .


, JavaPath . . .


JavaPath


public Object evalPath(String path, Object root, Object... values);

evalPath


  • — Java
  • A — b
  • , . — — name

, . C. .


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

. .


A a = new A();
JavaPath javaPath = new JavaPath(A.class);
public void setNameService(String name) {
    javaPath.evalPath("b.c.setName", a, name);
}

JavaPath , , , :


    javaPath.evalPath("b.c.setName($)", a, name);

$ $0 — .



a0.a1.… .an



a0.a1.… .an-1


, , / null. an . , , , evalPath. , . JavaPath .


JavaPath


JavaPath , . . . , , , . , , ,
Java . , , , API.



Gráfico de sintaxis



JavaPath . . , , , . . , , , .. — .


$ #


Parámetros especiales



, evalPath $[:digit:]* . $ , . .


.


JavaPath
"a($)",
"a($0)"
"a($1.name)"name,


. : #[:digit:]* # #0


.


JavaPath
"a(#)"
"a(#0.name)"name
"a.b(#1)"'a'

, -.


public class A {
    A parent;
    A child;
    String name;
    public A(A parent) {
        this.parent = parent;
    }
}

A a = new A(null);
JavaPath javaPath = new JavaPath(A.class);
javaPath.evalPath("name",a,"PARENT");
javaPath.evalPath("child(#0).name",a,"CHILD");
javaPath.evalPath("child(#0).child(#1).name",a,"GRAND-CHILD");
assertEquals("PARENT",a.name);
assertEquals("CHILD",a.child.name);
assertEquals("GRAND-CHILD",a.child.child.name);
assertEquals("CHILD",a.child.child.parent.name);
assertEquals("PARENT",a.child.child.parent.parent.name);

— .


"a.set('$0')" //  $0

InLine :


, JavaPath. , , . .


JavaPath
"a.b.c". , evalPath , .
"a.b.c($)", .
"a.b.c($0)"$0 $ .
"a.b.c('THE VALUE')"c 'THE VALUE' evalPath . .
"a().b().c",
"a().b.c".
"a.b(int 1024).c"
"a.b(Int 1024).c"Integer
"a.b(int 1024,' ').c",
a.setX(PhoneType CELL)enum PhoneType{HOME,CELL,WORK}, "CELL"

, , valueOf ( , enum ) .


, valueOf - , StringConverter, .



- null , . .


, , , . — . Java, .


"(T a).b"

: map .


public class A {
    Map<String,String> map;
}

A a = new A();
JavaPath javaPath = new JavaPath(A.class);
//       map
javaPath.evalPath("(HashMap map).put(firstName,$)", a, "John");
//    ,     .
javaPath.evalPath("map.put(lastName,$)", a, "Silver");

.


//  HashMap      .
//        0.8 
javaPath.evalPath("(HashMap map(int 100,float '0.8')).put(firstName,$)", a, "John");

, null. map .



enum PhoneType{HOME,CELL,WORK}
public static class A {
    String firstName;
    String lastName;
    Map<PhoneType, Set<String>> phones;
    Map<String, PhoneType> reversedPhones;
}

A a = new A();
ClassRegistry  classRegistry = new ClassRegistry();
classRegistry.registerClass(PhoneType.class,PhoneType.class.getSimpleName());
JavaPath javaPath = new JavaPath(A.class,classRegistry);

javaPath.evalPath("(map phones).put(PhoneType WORK)", a, new HashSet<>());
javaPath.evalPath("phones.computeIfAbsent(PhoneType HOME,key->new HashSet).@", a);
javaPath.evalPath("phones.computeIfAbsent(PhoneType CELL,key->new HashSet).@", a);
javaPath.evalPath("(map reversedPhones).@", a);

javaPath.evalPath("firstName", a, "John");
javaPath.evalPath("lastName", a, "Smith");

javaPath.evalPath("phones.get(PhoneType CELL).add", a, "1-101-111-2233");
javaPath.evalPath("phones.get(PhoneType HOME).add", a, "1-101-111-7865");
javaPath.evalPath("phones.get(PhoneType WORK).add", a, "1-105-333-1100");
javaPath.evalPath("phones.get(PhoneType WORK).add($)", a, "1-105-333-1104");

javaPath.evalPath("reversedPhones.put($,PhoneType CELL)", a, "1-101-111-2233");
javaPath.evalPath("reversedPhones.put($,PhoneType HOME)", a, "1-101-111-7865");
javaPath.evalPath("reversedPhones.put($,PhoneType WORK)", a, "1-105-333-1100");
javaPath.evalPath("reversedPhones.put($,PhoneType WORK)", a, "1-105-333-1104");

@


@ . , . .


||


null, JavaPath . .


JavaPath
"getA∣∣setA($1).name($0)"getA null setA, getA
"getA∣∣init.name($0)"

::


, -, ::


JavaPath
"(UserInfo::newInstance userInfo).phone.ext"UserInfo UserInfo.newInstance()
"(UserInfo::newInstance userInfo(John,Smith)).phone.ext"UserInfo UserInfo.newInstance(String a, String b)
"a.b(Integer::valueOf 100).c". .
"(HashMap::new map).get"- new . .

ClassRegistry


, , .. ClassRegistry , JavaPath.


ClassRegistry . ClassRegistry, JavaPath.


PhoneType


ClassRegistry  classRegistry = new ClassRegistry();
classRegistry.registerClass(PhoneType.class,PhoneType.class.getSimpleName(),"Phone");
JavaPath javaPath = new JavaPath(A.class,classRegistry);

PhoneType , , Phone.


ClassRegistry . , :: .


. ClassRegistry . , StringConverter — .


public class A {
...
static {
    ClassRegistry.registerGlobalStringConverter(A.class,A::stringToA); 
}
public static A stringToA(String str) {
       A a = new A("{"+str+"}"); // - 
       return a;
    }
}

public class B {
    A a;
}

JavaPath javaPath = new JavaPath(B.class); //  A::stringToA

@PathElement @NoPathElement


@PathElement .


public class A {
    String name; //       "name"
    @PathElement({"name","first_name","firstName"})
    public void setName(String name) {
        this.name = name;
    }
}

, setName "name", . .


@NoPathElement JavaPath.


public class A {
    StringBuilder stringBuilder = new StringBuilder();

    @NoPathElement
    private final String protectedField = "IMMUTABLE BY JAVA PATH!";

    public void add(String str) {
        stringBuilder.append(str == null ? "N/A" : str);
    }

    @NoPathElement
    public void add(Object val) {
        stringBuilder.append(val);
    }
}

.




JavaPath . .


public class A {
    String firstName;
    String lastName;
    int age;
}

A a = new A();
JavaPath javaPath = new JavaPath(A.class);
javaPath.evalPath("firstName; lastName; age", a, "John","Smith",55);
// $       ,    
javaPath.evalPath("firstName($); lastName($); age($)", a, "John","Smith",55);
//         .
javaPath.evalPath("firstName($0); lastName($1); age($2)", a, "John","Smith",55);

'$', , . , firstName($) "John" ( , ), age($) — 55 ( , ). .


, , .


. .



JavaPath


, . , ? initPath
.


JavaPath . , . , , root. # #0


initPath .


:


//      JavaPath.  
Object instanceOfA = javaPath.initPath("(com.my.project.A #0).b", "test");
//      initPath
A instanceOfA = javaPath.initPath(A.class, "#.b", "test");
//       , #  #0
A instanceOfA = javaPath.initPath(A.class, "root.b", "test");



El método setEnablePathCaching (boolean enableCaching) de la clase JavaPath le permite guardar el resultado del analizador en la memoria caché. No debe confundirse con el almacenamiento en caché no desactivable de jerarquías de campo y métodos de clase. La memoria caché de ruta está deshabilitada de forma predeterminada porque puede conducir a un consumo de memoria no controlado si las rutas se calculan dinámicamente.


Ejemplo: habrá tres rutas diferentes en el caché:


evalPath("user.name('John'));"
evalPath("user.name('Peter'));"
evalPath("user.name('Mike'));"

En su lugar, use explícitamente el paso de valores variables. El ejemplo inferior guardará una ruta.


evalPath("user.name($0)","John");
evalPath("user.name($0)","Peter");
evalPath("user.name($0)","Mike");

Dependencias


Java8 y mayores


Repositorio Maven


<dependency>
    <groupId>com.aegisql</groupId>
    <artifactId>java-path</artifactId>
    <version>0.2.0</version>
</dependency>

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