org.joda.beans.ser
Interface SerDeserializer

All Known Implementing Classes:

DefaultDeserializer

public interface SerDeserializer

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:

1. lookupMetaBean
2. createBuilder
3. lookupMetaProperty, then setValue - once per property
4. build

A renamed property can be handled by overriding the 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 lookupMetaProperty and 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 createBuilder and 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();
  }
 

findMetaBean

MetaBean findMetaBean(Class<?> beanType)

Lookup the meta-bean for the speecified type.

If the type is not a bean, then null may be returned.

Parameters:

beanType - the type being processed, not null

Returns:

the meta-bean, null if not a bean type

createBuilder

BeanBuilder<?> createBuilder(Class<?> beanType,
                             MetaBean metaBean)

Creates the stateful builder that captures state as the parse progresses.

This is normally a BeanBuilder however any type may be returned.

Parameters:

beanType - the type being processed, not null

metaBean - the meta-bean, null if not a bean type

Returns:

the builder, null if not interested in the parse progress

findMetaProperty

MetaProperty<?> findMetaProperty(Class<?> beanType,
                                 MetaBean metaBean,
                                 String propertyName)

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.

Parameters:

beanType - the type being processed, not null

metaBean - the meta-bean, null if not a bean type

propertyName - the property name being parsed, not null

Returns:

the meta-property, null to ignore the property

setValue

void setValue(BeanBuilder<?> builder,
              MetaProperty<?> metaProp,
              Object value)

Sets the parsed value into the builder.

Parameters:

builder - the builder, null if not interested in the parse progress

metaProp - the meta-property, not null

value - the parsed value, may be null

build

Object build(Class<?> beanType,
             BeanBuilder<?> builder)

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.

Parameters:

beanType - the type being processed, not null

builder - the builder, null if not interested in the parse progress

Returns:

the final built object, may be null