ObjectCodec.java
/* Jackson JSON-processor.
*
* Copyright (c) 2007- Tatu Saloranta, tatu.saloranta@iki.fi
*/
package com.fasterxml.jackson.core;
import java.io.IOException;
import java.util.Iterator;
import com.fasterxml.jackson.core.type.ResolvedType;
import com.fasterxml.jackson.core.type.TypeReference;
/**
* Abstract class that defines the interface that {@link JsonParser} and
* {@link JsonGenerator} use to serialize and deserialize regular
* Java objects (POJOs aka Beans).
*<p>
* The standard implementation of this class is
* <code>com.fasterxml.jackson.databind.ObjectMapper</code>,
* defined in the "jackson-databind".
*/
public abstract class ObjectCodec
extends TreeCodec // since 2.3
implements Versioned // since 2.3
{
protected ObjectCodec() { }
// Since 2.3
@Override
public abstract Version version();
/*
/**********************************************************
/* API for de-serialization (JSON-to-Object)
/**********************************************************
*/
/**
* Method to deserialize JSON content into a non-container
* type (it can be an array type, however): typically a bean, array
* or a wrapper type (like {@link java.lang.Boolean}).
*<p>
* Note: this method should NOT be used if the result type is a
* container ({@link java.util.Collection} or {@link java.util.Map}.
* The reason is that due to type erasure, key and value types
* can not be introspected when using this method.
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueType Java value type to bind content to
*
* @return Value deserialized
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> T readValue(JsonParser p, Class<T> valueType)
throws IOException;
/**
* Method to deserialize JSON content into a Java type, reference
* to which is passed as argument. Type is passed using so-called
* "super type token"
* and specifically needs to be used if the root type is a
* parameterized (generic) container type.
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueTypeRef Java value type to bind content to
*
* @return Value deserialized
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> T readValue(JsonParser p, TypeReference<T> valueTypeRef)
throws IOException;
/**
* Method to deserialize JSON content into a POJO, type specified
* with fully resolved type object (so it can be a generic type,
* including containers like {@link java.util.Collection} and
* {@link java.util.Map}).
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueType Java value type to bind content to
*
* @return Value deserialized
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> T readValue(JsonParser p, ResolvedType valueType)
throws IOException;
/**
* Method for reading sequence of Objects from parser stream,
* all with same specified value type.
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueType Java value type to bind content to
*
* @return Iterator for incrementally deserializing values
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> Iterator<T> readValues(JsonParser p, Class<T> valueType)
throws IOException;
/**
* Method for reading sequence of Objects from parser stream,
* all with same specified value type.
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueTypeRef Java value type to bind content to
*
* @return Iterator for incrementally deserializing values
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> Iterator<T> readValues(JsonParser p, TypeReference<T> valueTypeRef)
throws IOException;
/**
* Method for reading sequence of Objects from parser stream,
* all with same specified value type.
*
* @param <T> Nominal parameter for target type
*
* @param p Parser to use for decoding content to bind
* @param valueType Java value type to bind content to
*
* @return Iterator for incrementally deserializing values
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
public abstract <T> Iterator<T> readValues(JsonParser p, ResolvedType valueType)
throws IOException;
/*
/**********************************************************
/* API for serialization (Object-to-JSON)
/**********************************************************
*/
/**
* Method to serialize given Java Object, using generator
* provided.
*
* @param gen Generator to use for serializing value
* @param value Value to serialize
*
* @throws IOException for low-level write issues, or
* {@link JsonGenerationException} for decoding problems
*/
public abstract void writeValue(JsonGenerator gen, Object value) throws IOException;
/*
/**********************************************************
/* TreeCodec pass-through methods
/**********************************************************
*/
/**
* Method for deserializing JSON content as tree expressed
* using set of {@link TreeNode} instances. Returns
* root of the resulting tree (where root can consist
* of just a single node if the current event is a
* value event, not container). Empty or whitespace
* documents return null.
*
* @return next tree from {@code p}, or {@code null} if empty.
*
* @throws IOException for low-level read issues, or
* {@link JsonParseException} for decoding problems
*/
@Override
public abstract <T extends TreeNode> T readTree(JsonParser p) throws IOException;
/**
* Method for serializing JSON content from given Tree instance, using
* specified generator.
*
* @param gen Generator to use for serializing value
* @param tree Tree to serialize
*
* @throws IOException for low-level write issues, or
* {@link JsonGenerationException} for decoding problems
*/
@Override
public abstract void writeTree(JsonGenerator gen, TreeNode tree) throws IOException;
/**
* Method for construct root level Object nodes
* for Tree Model instances.
*
* @return Object node created
*/
@Override
public abstract TreeNode createObjectNode();
/**
* Method for construct root level Array nodes
* for Tree Model instances.
*
* @return Array node created
*/
@Override
public abstract TreeNode createArrayNode();
/**
* Method for constructing a {@link JsonParser} for reading
* contents of a JSON tree, as if it was external serialized
* JSON content.
*
* @param n Content to traverse over
*
* @return Parser constructed for traversing over contents of specified node
*/
@Override
public abstract JsonParser treeAsTokens(TreeNode n);
/*
/**********************************************************
/* Extended tree conversions beyond TreeCodec
/**********************************************************
*/
/**
* Convenience method for converting given JSON tree into instance of specified
* value type. This is equivalent to first constructing a {@link JsonParser} to
* iterate over contents of the tree, and using that parser for data binding.
*
* @param <T> Nominal parameter for target type
*
* @param n Tree to convert
* @param valueType Java target value type to convert content to
*
* @return Converted value instance
*
* @throws JsonProcessingException if structural conversion fails
*/
public abstract <T> T treeToValue(TreeNode n, Class<T> valueType)
throws JsonProcessingException;
/*
/**********************************************************
/* Basic accessors
/**********************************************************
*/
/**
* @deprecated Use {@link #getFactory} instead.
*
* @return Underlying {@link JsonFactory} instance
*/
@Deprecated
public JsonFactory getJsonFactory() { return getFactory(); }
/**
* Accessor for finding underlying data format factory
* ({@link JsonFactory}) codec will use for data binding.
*
* @return Underlying {@link JsonFactory} instance
*/
public JsonFactory getFactory() { return getJsonFactory(); }
}