io.permazen.core.Field Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
*/
package io.permazen.core;
import com.google.common.base.Preconditions;
import com.google.common.reflect.TypeToken;
import io.permazen.core.util.ObjIdMap;
import io.permazen.util.ByteWriter;
import io.permazen.util.UnsignedIntEncoder;
/**
* Represents a field in an {@link ObjType} or a ({@linkplain SimpleField simple}) sub-field of a {@link ComplexField}.
*
* @param Java type for the field's values
*/
public abstract class Field extends SchemaItem {
final TypeToken typeToken;
final byte[] encodedStorageId;
/**
* Constructor.
*
* @param name the name of the field
* @param storageId field storage ID
* @param schema schema version
* @param typeToken Java type for the field's values
* @throws IllegalArgumentException if any parameter is null
* @throws IllegalArgumentException if {@code name} is invalid
* @throws IllegalArgumentException if {@code storageId} is non-positive
*/
Field(String name, int storageId, Schema schema, TypeToken typeToken) {
super(name, storageId, schema);
Preconditions.checkArgument(typeToken != null, "null typeToken");
this.typeToken = typeToken;
this.encodedStorageId = UnsignedIntEncoder.encode(this.storageId);
}
// Public methods
/**
* Get the Java type corresponding to this field.
*
* @return this field's type
*/
public TypeToken getTypeToken() {
return this.typeToken;
}
/**
* Get the value of this field in the given object.
* Does not alter the schema version of the object.
*
* @param tx transaction
* @param id object id
* @return this field's value in the specified object
* @throws DeletedObjectException if no object with ID equal to {@code id} is found
* @throws UnknownTypeException if {@code id} specifies an unknown object type
* @throws UnknownFieldException if this field does not exist in the specified object
* @throws StaleTransactionException if this transaction is no longer usable
* @throws IllegalArgumentException if either parameter is null
* @throws IllegalArgumentException if this field is a sub-field of a {@link ComplexField}
*/
public abstract T getValue(Transaction tx, ObjId id);
/**
* Determine if this field in the specified object has its default value in the specified {@link Transaction}.
*
* @param tx {@link Transaction} containing field state
* @param id object ID
* @return true if this field is set to its initial default value in object {@code id}, otherwise false
* @throws DeletedObjectException if no object with ID equal to {@code id} is found
* @throws UnknownTypeException if {@code id} specifies an unknown object type
* @throws StaleTransactionException if this transaction is no longer usable
* @throws IllegalArgumentException if either parameter is null
* @throws IllegalArgumentException if this field is a sub-field of a {@link ComplexField}
*/
public abstract boolean hasDefaultValue(Transaction tx, ObjId id);
/**
* Apply visitor pattern.
*
* @param target target to invoke
* @param visitor return type
* @return value from the method of {@code target} corresponding to this instance's type
* @throws NullPointerException if {@code target} is null
*/
public abstract R visit(FieldSwitch target);
// Non-public methods
/**
* Copy field value between transactions.
*
*
* This method assumes both objects exist and both transactions are locked.
*/
abstract void copy(ObjId srcId, ObjId dstId, Transaction srcTx, Transaction dstTx, ObjIdMap objectIdMap);
/**
* Build the key (or key prefix) for this field in the given object.
*/
byte[] buildKey(ObjId id) {
final ByteWriter writer = new ByteWriter(ObjId.NUM_BYTES + this.encodedStorageId.length);
id.writeTo(writer);
writer.write(this.encodedStorageId);
return writer.getBytes();
}
/**
* Build the key (or key prefix) for a field with the given storage ID in the given object.
*/
static byte[] buildKey(ObjId id, int storageId) {
final ByteWriter writer = new ByteWriter(ObjId.NUM_BYTES + UnsignedIntEncoder.encodeLength(storageId));
id.writeTo(writer);
UnsignedIntEncoder.write(writer, storageId);
return writer.getBytes();
}
/**
* Determine if the given {@link Field} is equivalent to this one, or should be reset on an upgrade.
*/
abstract boolean isUpgradeCompatible(Field field);
}