使用Jackson将可选的序列化为字符串

I have a value object with an Optional<Integer> field. I want it to look like a string when it's serialized, but the Optional part is getting in the way.

我有一个具有可选的字段的值对象。当它被序列化时，我希望它看起来像一个字符串，但是可选部分阻碍了它。

I have the following class:

我有以下课程:

public class Person {
    private com.google.common.base.Optional<Integer> age;
    public com.google.common.base.Optional<Integer> getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = com.google.common.base.Optional.fromNullable(age);
    }
}

Here is my test:

这是我的测试:

@Test
public void testPerson() throws Exception {
    ObjectMapper objectMapper = new ObjectMapper().registerModule(new GuavaModule());
    Person person = new Person();
    person.setAge(1);
    String jsonString = objectMapper.writeValueAsString(person);
    assertEquals(jsonString, "{\"age\":\"1\"}");
}

It's failing with this output:

输出是失败的:

java.lang.AssertionError: expected [{"age":"1"}] but found [{"age":1}]

. lang。AssertionError: expected [{"age":"1"}]但是找到了[{"age":1}]

I have tried adding a @JsonSerialize annotation to the property, like this:

我尝试向属性添加一个@JsonSerialize注释，如下所示:

@JsonSerialize(using = ToStringSerializer.class)
private com.google.common.base.Optional<Integer> age;

But then the test fails like this:

但是测试失败了:

java.lang.AssertionError: expected [{"age":"1"}] but found [{"age":"Optional.of(1)"}]

. lang。AssertionError: expected [{"age":"1"}]但是找到了[{"age":"Optional.of(1)}]

I've been looking around in com.fasterxml.jackson.datatype.guava.ser.GuavaOptionalSerializer but I can't seem to figure out how to use it correctly, if even if it's meant to be used this way.

我一直在找com.fasterxml.jackson.datatype.guava.ser。GuavaOptionalSerializer，但我似乎不知道如何正确地使用它，即使它是用这种方式使用的。

What can I do to get this test working?

我该怎么做才能让这个测试有效呢?

P.S. If it were up to me, I would remove the Optional altogether, but that's not an option.

附注:如果由我决定，我会把可选选项全部删除，但那不是一个选项。

1 个解决方案

#1

I ended up creating my own simple serializer:

我最终创建了自己的简单序列化器:

public class OptionalStringSerializer extends JsonSerializer<Optional<Object>> {
    @Override
    public void serialize(Optional<Object> value, JsonGenerator gen,
            SerializerProvider serializers) throws IOException {
        gen.writeString(value.isPresent() ? value.get().toString() : null);
    }
}

This is how I specified it:

我是这样规定的:

@JsonSerialize(using = OptionalStringSerializer.class)
private com.google.common.base.Optional<Integer> age;

#1