org.joda.beans.ser.SerDeserializer Maven / Gradle / Ivy
/*
* Copyright 2001-present Stephen Colebourne
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.joda.beans.ser;
import org.joda.beans.BeanBuilder;
import org.joda.beans.MetaBean;
import org.joda.beans.MetaProperty;
/**
* Assists with deserialization allowing migration of data from an old data format to a new one.
*
* This allows beans stored under an old version to be read in by a newer version.
*
* Methods are called in order as follows:
*
* - {@code lookupMetaBean}
*
- {@code createBuilder}
*
- {@code lookupMetaProperty}, then {@code setValue} - once per property
*
- {@code build}
*
*
* A renamed property can be handled by overriding the {@code lookupMetaProperty}:
*
* public MetaProperty<?> findMetaProperty(Class<?> beanType, MetaBean metaBean, String propertyName) {
* if ("firstName".equals(propertyName)) {
* return metaBean.metaProperty("forename");
* }
* return super.findMetaProperty(beanType, metaBean, propertyName);
* }
*
*
* A property type change can be handled by overriding the {@code lookupMetaProperty}
* and {@code setValue}:
*
* private MetaProperty NUMBER_OF_CARS_STRING =
* StandaloneMetaProperty.of("numberOfCars", SimplePerson.meta(), String.class);
*
* public MetaProperty<?> findMetaProperty(Class<?> beanType, MetaBean metaBean, String propertyName) {
* if ("numberOfCars".equals(propertyName)) {
* return NUMBER_OF_CARS_STRING; // replica of the old property
* }
* return super.findMetaProperty(beanType, metaBean, propertyName);
* }
*
* public void setValue(BeanBuilder builder, MetaProperty metaProp, Object value) {
* if (metaProp == NUMBER_OF_CARS_STRING && value != null) {
* String oldValue = value.toString();
* switch (oldValue) {
* case "One": value = 1; break;
* case "Two": value = 2; break;
* case "Lots": value = 3; break;
* default: value = 0; break;
* }
* }
* super.setValue(builder, metaProp, value);
* }
*
*
* A semantic change can be handled by overriding the {@code createBuilder}
* and {@code build}, buffering the input to process at the end of the bean:
*
* public BeanBuilder createBuilder(Class beanType, MetaBean metaBean) {
* return BufferingBeanBuilder.of(metaBean);
* }
*
* public Object build(Class<?> beanType, BeanBuilder<?> builder) {
* BufferingBeanBuilder<?> bld = (BufferingBeanBuilder<?>) builder;
* if ("Stephen".equals(bld.getBuffer().get(SimplePerson.meta().forename())) &&
* "Colebourne".equals(bld.getBuffer().get(SimplePerson.meta().surname()))) {
* bld.set(SimplePerson.meta().forename(), "Steve");
* }
* return bld.build();
* }
*
*
* @author Stephen Colebourne
*/
public interface SerDeserializer {
/**
* Lookup the meta-bean for the speecified type.
*
* If the type is not a bean, then null may be returned.
*
* @param beanType the type being processed, not null
* @return the meta-bean, null if not a bean type
*/
public abstract MetaBean findMetaBean(Class beanType);
/**
* Creates the stateful builder that captures state as the parse progresses.
*
* This is normally a {@code BeanBuilder} however any type may be returned.
*
* @param beanType the type being processed, not null
* @param metaBean the meta-bean, null if not a bean type
* @return the builder, null if not interested in the parse progress
*/
public abstract BeanBuilder createBuilder(Class beanType, MetaBean metaBean);
/**
* Lookup the meta-property for the specified property name.
*
* Return null if a property has been deleted, which will cause the parser
* to discard the property.
*
* Return a non-null meta-property to parse the property.
* If the property was renamed, or had a type change, then the meta-property
* should match the property as originally stored.
*
* @param beanType the type being processed, not null
* @param metaBean the meta-bean, null if not a bean type
* @param propertyName the property name being parsed, not null
* @return the meta-property, null to ignore the property
*/
public abstract MetaProperty findMetaProperty(Class beanType, MetaBean metaBean, String propertyName);
/**
* Sets the parsed value into the builder.
*
* @param builder the builder, null if not interested in the parse progress
* @param metaProp the meta-property, not null
* @param value the parsed value, may be null
*/
public abstract void setValue(BeanBuilder builder, MetaProperty metaProp, Object value);
/**
* Builds the resulting object.
*
* This method finishes the builder and returns the final object.
* The migrator could validate or manipulate data here once all data is parsed,
* for example to default a missing field.
*
* @param beanType the type being processed, not null
* @param builder the builder, null if not interested in the parse progress
* @return the final built object, may be null
*/
public abstract Object build(Class beanType, BeanBuilder builder);
}