Object Mapping Framework

/**
 * Declarative parser for objects with setter-based construction
 * @param <Value> the type of object to parse
 * @param <Context> the type of parsing context
 */
public final class ObjectParser<Value, Context> extends AbstractObjectParser<Value, Context> {
    
    /**
     * Create an object parser with automatic value creation
     * @param name parser name for error messages
     */
    public ObjectParser(String name);
    
    /**
     * Create an object parser with custom value supplier
     * @param name parser name for error messages
     * @param valueSupplier supplier to create new instances
     */
    public ObjectParser(String name, Supplier<Value> valueSupplier);
    
    /**
     * Create an object parser with unknown field handling
     * @param name parser name for error messages
     * @param ignoreUnknownFields whether to ignore unknown fields
     * @param valueSupplier supplier to create new instances
     */
    public ObjectParser(String name, boolean ignoreUnknownFields, Supplier<Value> valueSupplier);
    
    /**
     * Parse content into a new object instance
     * @param parser content parser
     * @param context parsing context
     * @return parsed object
     */
    public Value parse(XContentParser parser, Context context) throws IOException;
    
    /**
     * Parse content into an existing object instance
     * @param parser content parser
     * @param value existing object to populate
     * @param context parsing context
     * @return the populated object
     */
    public Value parse(XContentParser parser, Value value, Context context) throws IOException;
}

/**
 * Declare a string field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareString(BiConsumer<Value, String> consumer, ParseField field);

/**
 * Declare an integer field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareInt(BiConsumer<Value, Integer> consumer, ParseField field);

/**
 * Declare a long field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareLong(BiConsumer<Value, Long> consumer, ParseField field);

/**
 * Declare a float field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareFloat(BiConsumer<Value, Float> consumer, ParseField field);

/**
 * Declare a double field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareDouble(BiConsumer<Value, Double> consumer, ParseField field);

/**
 * Declare a boolean field
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareBoolean(BiConsumer<Value, Boolean> consumer, ParseField field);

/**
 * Declare an object field
 * @param consumer setter method reference
 * @param parser parser for the object type
 * @param field parse field definition
 */
public <T> void declareObject(BiConsumer<Value, T> consumer, ContextParser<Context, T> parser, ParseField field);

/**
 * Declare an array of objects field
 * @param consumer setter method reference
 * @param parser parser for individual array elements
 * @param field parse field definition
 */
public <T> void declareObjectArray(BiConsumer<Value, List<T>> consumer, ContextParser<Context, T> parser, ParseField field);

/**
 * Declare a named object field (using registry)
 * @param consumer setter method reference
 * @param namedObjectParser parser for named objects
 * @param field parse field definition
 */
public <T> void declareNamedObject(BiConsumer<Value, T> consumer, 
                                   NamedObjectParser<T, Context> namedObjectParser, ParseField field);

/**
 * Declare an array of named objects field
 * @param consumer setter method reference
 * @param namedObjectParser parser for individual named objects
 * @param field parse field definition
 */
public <T> void declareNamedObjects(BiConsumer<Value, List<T>> consumer,
                                    NamedObjectParser<T, Context> namedObjectParser, ParseField field);

/**
 * Declare a field that can contain any type of value
 * @param consumer setter method reference
 * @param field parse field definition
 */
public void declareField(BiConsumer<Value, Object> consumer, ContextParser<Context, Object> parser, 
                        ParseField field, ValueType expectedValueType);

import org.elasticsearch.xcontent.*;

// Define a simple data class
public class User {
    private String name;
    private int age;
    private boolean active;
    private List<String> skills;
    private Address address;
    
    // Constructor, getters, and setters...
    public User() {}
    public void setName(String name) { this.name = name; }
    public void setAge(int age) { this.age = age; }
    public void setActive(boolean active) { this.active = active; }
    public void setSkills(List<String> skills) { this.skills = skills; }
    public void setAddress(Address address) { this.address = address; }
}

public class Address {
    private String street;
    private String city;
    
    public Address() {}
    public void setStreet(String street) { this.street = street; }
    public void setCity(String city) { this.city = city; }
}

// Create parsers
ObjectParser<Address, Void> addressParser = new ObjectParser<>("address", Address::new);
addressParser.declareString(Address::setStreet, new ParseField("street"));
addressParser.declareString(Address::setCity, new ParseField("city"));

ObjectParser<User, Void> userParser = new ObjectParser<>("user", User::new);
userParser.declareString(User::setName, new ParseField("name"));
userParser.declareInt(User::setAge, new ParseField("age"));
userParser.declareBoolean(User::setActive, new ParseField("active"));
userParser.declareStringArray(User::setSkills, new ParseField("skills"));
userParser.declareObject(User::setAddress, addressParser, new ParseField("address"));

// Parse JSON content
String json = """
{
    "name": "John Doe",
    "age": 30,
    "active": true,
    "skills": ["Java", "Elasticsearch"],
    "address": {
        "street": "123 Main St",
        "city": "New York"
    }
}
""";

XContentParser parser = XContentType.JSON.xContent()
    .createParser(XContentParserConfiguration.EMPTY, json);
User user = userParser.parse(parser, null);
parser.close();

/**
 * Parser for objects requiring constructor arguments
 * @param <Value> the type of object to construct
 * @param <Context> the type of parsing context
 */
public final class ConstructingObjectParser<Value, Context> extends AbstractObjectParser<Value, Context> {
    
    /**
     * Create a constructing parser with simple builder function
     * @param name parser name for error messages
     * @param builder function that constructs objects from argument array
     */
    public ConstructingObjectParser(String name, Function<Object[], Value> builder);
    
    /**
     * Create a constructing parser with context-aware builder function
     * @param name parser name for error messages
     * @param ignoreUnknownFields whether to ignore unknown fields
     * @param builder function that constructs objects from arguments and context
     */
    public ConstructingObjectParser(String name, boolean ignoreUnknownFields, 
                                   BiFunction<Object[], Context, Value> builder);
    
    /**
     * Mark a field as a required constructor argument
     * @return BiConsumer that marks the field as a constructor argument
     */
    public static <Value, FieldT> BiConsumer<Value, FieldT> constructorArg();
    
    /**
     * Mark a field as an optional constructor argument
     * @return BiConsumer that marks the field as an optional constructor argument
     */
    public static <Value, FieldT> BiConsumer<Value, FieldT> optionalConstructorArg();
    
    /**
     * Parse content into a new object instance
     * @param parser content parser
     * @param context parsing context
     * @return constructed object
     */
    public Value parse(XContentParser parser, Context context) throws IOException;
}

// Immutable data class with constructor
public class ImmutableUser {
    private final String name;
    private final int age;
    private final boolean active;
    private final List<String> skills;
    
    public ImmutableUser(String name, int age, boolean active, List<String> skills) {
        this.name = name;
        this.age = age;
        this.active = active;
        this.skills = skills;
    }
    
    // Getters only...
}

// Create constructing parser
ConstructingObjectParser<ImmutableUser, Void> parser = new ConstructingObjectParser<>(
    "immutable_user",
    args -> new ImmutableUser(
        (String) args[0],    // name
        (Integer) args[1],   // age
        (Boolean) args[2],   // active
        (List<String>) args[3]  // skills
    )
);

// Declare fields as constructor arguments
parser.declareString(constructorArg(), new ParseField("name"));
parser.declareInt(constructorArg(), new ParseField("age"));
parser.declareBoolean(constructorArg(), new ParseField("active"));
parser.declareStringArray(constructorArg(), new ParseField("skills"));

// Parse content
XContentParser contentParser = XContentType.JSON.xContent()
    .createParser(XContentParserConfiguration.EMPTY, jsonContent);
ImmutableUser user = parser.parse(contentParser, null);
contentParser.close();

/**
 * Parser that uses reflection for object construction
 * @param <Value> the type of object to instantiate
 * @param <Context> the type of parsing context
 */
public class InstantiatingObjectParser<Value, Context> 
    implements BiFunction<XContentParser, Context, Value>, ContextParser<Context, Value> {
    
    /**
     * Builder for creating instantiating parsers
     */
    public static class Builder<Value, Context> {
        
        /**
         * Create a builder for the specified class
         * @param name parser name for error messages
         * @param valueClass class to instantiate
         * @return builder instance
         */
        public static <Value, Context> Builder<Value, Context> builder(String name, Class<Value> valueClass);
        
        /**
         * Create a builder with unknown field handling
         * @param name parser name for error messages
         * @param ignoreUnknownFields whether to ignore unknown fields
         * @param valueClass class to instantiate
         * @return builder instance
         */
        public static <Value, Context> Builder<Value, Context> builder(String name, boolean ignoreUnknownFields, 
                                                                       Class<Value> valueClass);
        
        /**
         * Build the parser
         * @return InstantiatingObjectParser instance
         */
        public InstantiatingObjectParser<Value, Context> build();
    }
    
    /**
     * Parse content and instantiate object
     * @param parser content parser
     * @param context parsing context
     * @return instantiated object
     */
    public Value apply(XContentParser parser, Context context);
}

/**
 * Annotation to mark constructors for automatic parsing
 */
@Target(ElementType.CONSTRUCTOR)
@Retention(RetentionPolicy.RUNTIME)
public @interface ParserConstructor {
}

// Data class with annotated constructor
public class AnnotatedUser {
    private final String name;
    private final int age;
    private final boolean active;
    
    @ParserConstructor
    public AnnotatedUser(String name, int age, boolean active) {
        this.name = name;
        this.age = age;
        this.active = active;
    }
    
    // Getters...
}

// Create instantiating parser
InstantiatingObjectParser<AnnotatedUser, Void> parser = 
    InstantiatingObjectParser.builder("annotated_user", AnnotatedUser.class).build();

// Parse content (field names must match constructor parameter names)
XContentParser contentParser = XContentType.JSON.xContent()
    .createParser(XContentParserConfiguration.EMPTY, jsonContent);
AnnotatedUser user = parser.apply(contentParser, null);
contentParser.close();

/**
 * Enumeration of supported value types for object parsing
 */
public enum ValueType {
    STRING,
    STRING_OR_NULL,
    FLOAT,
    FLOAT_OR_NULL,
    DOUBLE,
    DOUBLE_OR_NULL,
    INT,
    INT_OR_NULL,
    LONG,
    LONG_OR_NULL,
    BOOLEAN,
    BOOLEAN_OR_NULL,
    STRING_ARRAY,
    FLOAT_ARRAY,
    DOUBLE_ARRAY,
    INT_ARRAY,
    LONG_ARRAY,
    BOOLEAN_ARRAY,
    OBJECT,
    OBJECT_OR_NULL,
    OBJECT_ARRAY,
    OBJECT_ARRAY_OR_NULL,
    VALUE,
    VALUE_OR_NULL,
    VALUE_ARRAY
}

/**
 * Interface for parsing objects with context
 */
@FunctionalInterface
public interface ContextParser<Context, T> {
    /**
     * Parse an object with the given context
     * @param parser content parser
     * @param context parsing context
     * @return parsed object
     */
    T parse(XContentParser parser, Context context) throws IOException;
}

/**
 * Interface for parsing named objects
 */
public interface NamedObjectParser<T, Context> {
    /**
     * Parse a named object
     * @param parser content parser
     * @param context parsing context
     * @param name object name
     * @return parsed object
     */
    T parse(XContentParser parser, Context context, String name) throws IOException;
}

/**
 * Interface for consuming unknown fields during parsing
 */
@FunctionalInterface
public interface UnknownFieldConsumer<Value> {
    /**
     * Accept an unknown field
     * @param objectParser the parser that encountered the unknown field
     * @param value the object being parsed
     * @param fieldName the unknown field name
     * @param parser content parser positioned at the field value
     */
    void accept(ObjectParser<Value, ?> objectParser, Value value, String fieldName, XContentParser parser);
}