com.fasterxml.jackson.databind.deser.ValueInstantiator Maven / Gradle / Ivy
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package com.fasterxml.jackson.databind.deser;
import java.io.IOException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.introspect.AnnotatedParameter;
import com.fasterxml.jackson.databind.introspect.AnnotatedWithParams;
/**
* Class that defines simple API implemented by objects that create value
* instances. Some or all of properties of value instances may
* be initialized by instantiator, rest being populated by deserializer,
* to which value instance is passed.
* Since different kinds of JSON values (structured and scalar)
* may be bound to Java values, in some cases instantiator
* fully defines resulting value; this is the case when JSON value
* is a scalar value (String, number, boolean).
*
* Note that this type is not parameterized (even though it would seemingly
* make sense), because such type information can not be use effectively
* during runtime: access is always using either wildcard type, or just
* basic {@link java.lang.Object}; and so adding type parameter seems
* like unnecessary extra work.
*
* Actual implementations are strongly recommended to be based on
* {@link com.fasterxml.jackson.databind.deser.std.StdValueInstantiator}
* which implements all methods, and as such will be compatible
* across versions even if new methods were added to this interface.
*/
public abstract class ValueInstantiator
{
/*
/**********************************************************
/* Metadata accessors
/**********************************************************
*/
/**
* Method that returns description of the value type this instantiator
* handles. Used for error messages, diagnostics.
*/
public abstract String getValueTypeDesc();
/**
* Method that will return true if any of canCreateXxx method
* returns true: that is, if there is any way that an instance could
* be created.
*/
public boolean canInstantiate() {
return canCreateUsingDefault() || canCreateUsingDelegate()
|| canCreateFromObjectWith() || canCreateFromString()
|| canCreateFromInt() || canCreateFromLong()
|| canCreateFromDouble() || canCreateFromBoolean();
}
/**
* Method that can be called to check whether a String-based creator
* is available for this instantiator
*/
public boolean canCreateFromString() { return false; }
/**
* Method that can be called to check whether an integer (int, Integer) based
* creator is available to use (to call {@link #createFromInt}).
*/
public boolean canCreateFromInt() { return false; }
/**
* Method that can be called to check whether a long (long, Long) based
* creator is available to use (to call {@link #createFromLong}).
*/
public boolean canCreateFromLong() { return false; }
/**
* Method that can be called to check whether a double (double / Double) based
* creator is available to use (to call {@link #createFromDouble}).
*/
public boolean canCreateFromDouble() { return false; }
/**
* Method that can be called to check whether a double (boolean / Boolean) based
* creator is available to use (to call {@link #createFromDouble}).
*/
public boolean canCreateFromBoolean() { return false; }
/**
* Method that can be called to check whether a default creator (constructor,
* or no-arg static factory method)
* is available for this instantiator
*/
public boolean canCreateUsingDefault() { return getDefaultCreator() != null; }
/**
* Method that can be called to check whether a delegate-based creator (single-arg
* constructor or factory method)
* is available for this instantiator
*/
public boolean canCreateUsingDelegate() { return false; }
/**
* Method that can be called to check whether a property-based creator
* (argument-taking constructor or factory method)
* is available to instantiate values from JSON Object
*/
public boolean canCreateFromObjectWith() { return false; }
/**
* Method called to determine types of instantiation arguments
* to use when creating instances with creator arguments
* (when {@link #canCreateFromObjectWith()} returns true).
* These arguments are bound from JSON, using specified
* property types to locate deserializers.
*
* NOTE: all properties will be of type
* {@link com.fasterxml.jackson.databind.deser.CreatorProperty}.
*/
public SettableBeanProperty[] getFromObjectArguments(DeserializationConfig config) { return null; }
/**
* Method that can be used to determine what is the type of delegate
* type to use, if any; if no delegates are used, will return null.
* If non-null type is returned, deserializer will bind JSON into
* specified type (using standard deserializer for that type), and
* pass that to instantiator.
*/
public JavaType getDelegateType(DeserializationConfig config) { return null; }
/*
/**********************************************************
/* Instantiation methods for JSON Object
/**********************************************************
*/
/**
* Method called to create value instance from a JSON value when
* no data needs to passed to creator (constructor, factory method);
* typically this will call the default constructor of the value object.
* It will only be used if more specific creator methods are not
* applicable; hence "default".
*
* This method is called if {@link #getFromObjectArguments} returns
* null or empty List.
*/
public Object createUsingDefault(DeserializationContext ctxt) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "
+getValueTypeDesc()+"; no default creator found");
}
/**
* Method called to create value instance from JSON Object when
* instantiation arguments are passed; this is done, for example when passing information
* specified with "Creator" annotations.
*
* This method is called if {@link #getFromObjectArguments} returns
* a non-empty List of arguments.
*/
public Object createFromObjectWith(DeserializationContext ctxt, Object[] args) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "+getValueTypeDesc()+" with arguments");
}
/**
* Method to called to create value instance from JSON Object using
* an intermediate "delegate" value to pass to createor method
*/
public Object createUsingDelegate(DeserializationContext ctxt, Object delegate) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "+getValueTypeDesc()+" using delegate");
}
/*
/**********************************************************
/* Instantiation methods for JSON scalar types
/* (String, Number, Boolean)
/**********************************************************
*/
public Object createFromString(DeserializationContext ctxt, String value) throws IOException {
return _createFromStringFallbacks(ctxt, value);
}
public Object createFromInt(DeserializationContext ctxt, int value) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "
+getValueTypeDesc()+" from Integer number ("+value+", int)");
}
public Object createFromLong(DeserializationContext ctxt, long value) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "
+getValueTypeDesc()+" from Integer number ("+value+", long)");
}
public Object createFromDouble(DeserializationContext ctxt, double value) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "
+getValueTypeDesc()+" from Floating-point number ("+value+", double)");
}
public Object createFromBoolean(DeserializationContext ctxt, boolean value) throws IOException {
throw ctxt.mappingException("Can not instantiate value of type "
+getValueTypeDesc()+" from Boolean value ("+value+")");
}
/*
/**********************************************************
/* Accessors for underlying creator objects (optional)
/**********************************************************
*/
/**
* Method that can be called to try to access member (constructor,
* static factory method) that is used as the "default creator"
* (creator that is called without arguments; typically default
* [zero-argument] constructor of the type).
* Note that implementations not required to return actual object
* they use (or, they may use some other instantiation) method.
* That is, even if {@link #canCreateUsingDefault()} returns true,
* this method may return null .
*/
public AnnotatedWithParams getDefaultCreator() { return null; }
/**
* Method that can be called to try to access member (constructor,
* static factory method) that is used as the "delegate creator".
* Note that implementations not required to return actual object
* they use (or, they may use some other instantiation) method.
* That is, even if {@link #canCreateUsingDelegate()} returns true,
* this method may return null .
*/
public AnnotatedWithParams getDelegateCreator() { return null; }
/**
* Method that can be called to try to access member (constructor,
* static factory method) that is used as the "non-default creator"
* (constructor or factory method that takes one or more arguments).
* Note that implementations not required to return actual object
* they use (or, they may use some other instantiation) method.
* That is, even if {@link #canCreateFromObjectWith()} returns true,
* this method may return null .
*/
public AnnotatedWithParams getWithArgsCreator() { return null; }
/**
* If an incomplete creator was found, this is the first parameter that
* needs further annotation to help make the creator complete.
*/
public AnnotatedParameter getIncompleteParameter() { return null; }
/*
/**********************************************************
/* Helper methods
/**********************************************************
*/
/**
* @since 2.4 (demoted from StdValueInstantiator)
*/
protected Object _createFromStringFallbacks(DeserializationContext ctxt, String value)
throws IOException, JsonProcessingException
{
/* 28-Sep-2011, tatu: Ok this is not clean at all; but since there are legacy
* systems that expect conversions in some cases, let's just add a minimal
* patch (note: same could conceivably be used for numbers too).
*/
if (canCreateFromBoolean()) {
String str = value.trim();
if ("true".equals(str)) {
return createFromBoolean(ctxt, true);
}
if ("false".equals(str)) {
return createFromBoolean(ctxt, false);
}
}
// also, empty Strings might be accepted as null Object...
if (value.length() == 0) {
if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)) {
return null;
}
}
throw ctxt.mappingException("Can not instantiate value of type "+getValueTypeDesc()
+" from String value ('"+value+"'); no single-String constructor/factory method");
}
}