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NullPointerException when trying to define a custom PropertyMap

由 女生的网名这么多〃 提交于 2019-11-29 14:55:28

I think this is ultimately due to the fact that ModelMapper can not instantiate TimeZone objects (nor LocalDateTime etc.) at the time of configuring the mapper.

Actually you don't have to configure anything.

ModelMapper mapper = new ModelMapper();

Foo foo = new Foo();
foo.setTimeZone(TimeZone.getDefault());

FooModel model = mapper.map(foo, FooModel.class);
System.out.println(model.getTimeZoneId()); // "Europe/Berlin" here

This works for me. ModelMapper found out that you want to map the TimeZone's property ID to FooModel's property timeZoneId.

Nevertheless, just in case you want to do that manually: Following the docs quickly, I found the concept of converters. Using a Converter which converts TimeZone to String you can do this:

ModelMapper mapper = new ModelMapper();
TypeMap<Foo, FooModel> typeMap = mapper.createTypeMap(Foo.class, FooModel.class);
Converter<TimeZone, String> tzConverter = ctx -> ctx.getSource().getID() + "!!!";
typeMap.addMappings(map -> {
    map.using(tzConverter).map(Foo::getTimeZone, FooModel::setTimeZoneId);
});

Foo foo = new Foo();
foo.setTimeZone(TimeZone.getDefault());

FooModel model = mapper.map(foo, FooModel.class);
System.out.println(model.getTimeZoneId()); // "Europe/Berlin!!!" here

Autowire using constructor like 

public FooConverter(ModelMapper modelMapper){
   this.modelMapper = modelMapper;
}

also make sure your ModelMapper bean has been defined in your spring config class like below:

@Bean
public ModelMapper modelMapper() {
    return new ModelMapper();
}
标签
java
Spring
nullpointerexception
modelmapper
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