使用 Pageable 字段测试端点时出现 JsonMappingException

Question

我需要调用一个需要Pageable 字段的端点：

@GetMapping
public Page<ProductDTO> listProducts(Pageable pageable) {
    return productService.findProducts(pageable); 
}

在我的测试中，我有这个代码：

MultiValueMap<String, String> parameters = new LinkedMultiValueMap<>();
parameters.add("page", String.valueOf(0));
URI url = defaultURI(port, "/products", parameters);

ParameterizedTypeReference<RestResponsePage<ProductDTO>> type = new ParameterizedTypeReference<RestResponsePage<ProductDTO>>() {};
ResponseEntity<RestResponsePage<ProductDTO>> response = restTemplate.exchange(url.toString(), HttpMethod.GET, httpEntity, type);

PageImpl 不包含默认构造函数，因此为了避免这个问题，我创建了一个类似以下的类来传递给ParameterizedTypeReference：

@JsonIgnoreProperties(ignoreUnknown = true) @Getter @Setter
public class RestResponsePage<T> extends PageImpl<T> implements Serializable {

    private static final long serialVersionUID = 3844794233375694591L;

    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    public RestResponsePage(@JsonProperty("content") List<T> content,
                        @JsonProperty("number") int page,
                        @JsonProperty("size") int size,
                        @JsonProperty("totalElements") long totalElements) {
        super(content, new PageRequest(page, size), totalElements);
    }

    public RestResponsePage(List<T> content, Pageable pageable, long totalElements) {
        super(content, pageable, totalElements);
    }

    public RestResponsePage(List<T> content) {
        super(content);
    }

    public RestResponsePage() {
        super(new ArrayList<T>());
    }
}

问题是我仍然收到以下错误：

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of org.springframework.data.domain.Pageable: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [Source: java.io.PushbackInputStream@75564689; line: 38, column: 16] (through reference chain: com.shaunyl.util.ResponsePageImpl["pageable"])

为什么它一直说我正在传递一个抽象类？ ResponsePageImpl 是一个类而不是抽象类。

谢谢

Answer 1

我找到了一种更优雅的方法来解决这个问题。其实是jackson序列化的问题。

首先定义一个jackson的模块：

public class PageJacksonModule extends Module {

    @Override
    public String getModuleName() {
        return "PageJacksonModule";
    }

    @Override
    public Version version() {
        return new Version(0,1,0, "", null,null);
    }

    @Override
    public void setupModule(SetupContext context) {
        context.setMixInAnnotations(Page.class, PageMixIn.class);
    }

    @JsonDeserialize(as = SimplePageImpl.class)
    private interface PageMixIn{ }


    static class SimplePageImpl<T> implements Page<T> {

        private final Page<T> delegate;

        public SimplePageImpl(
                @JsonProperty("content") List<T> content,
                @JsonProperty("page")int number,
                @JsonProperty("size") int size,
                @JsonProperty("totalElements") long totalElements){
            delegate = new PageImpl<>(content, PageRequest.of(number, size), totalElements);
        }


        @JsonProperty
        @Override
        public int getTotalPages() {
            return delegate.getTotalPages();
        }

        @JsonProperty
        @Override
        public long getTotalElements() {
            return delegate.getTotalElements();
        }

        @JsonProperty("page")
        @Override
        public int getNumber() {
            return delegate.getNumber();
        }

        @JsonProperty
        @Override
        public int getSize() {
            return delegate.getSize();
        }

        @JsonProperty
        @Override
        public int getNumberOfElements() {
            return delegate.getNumberOfElements();
        }

        @JsonProperty
        @Override
        public List<T> getContent() {
            return delegate.getContent();
        }

        @JsonProperty
        @Override
        public boolean hasContent() {
            return delegate.hasContent();
        }

        @JsonIgnore
        @Override
        public Sort getSort() {
            return delegate.getSort();
        }

        @JsonProperty
        @Override
        public boolean isFirst() {
            return delegate.isFirst();
        }

        @JsonProperty
        @Override
        public boolean isLast() {
            return delegate.isLast();
        }

        @JsonIgnore
        @Override
        public boolean hasNext() {
            return delegate.hasNext();
        }

        @JsonIgnore
        @Override
        public boolean hasPrevious() {
            return delegate.hasPrevious();
        }

        @JsonIgnore
        @Override
        public Pageable nextPageable() {
            return delegate.nextPageable();
        }
        
        @JsonIgnore
        @Override
        public Pageable previousPageable() {
            return delegate.previousPageable();
        }
        
        @JsonIgnore
        @Override
        public <U> Page<U> map(Function<? super T, ? extends U> converter) {
            return delegate.map(converter);
        }

        @JsonIgnore
        @Override
        public Iterator<T> iterator() {
            return delegate.iterator();
        }
    }
}

然后注入它：

@Configuration
public class JacksonConfig {

    @Bean
    public Module pageJacksonModule() {
        return new PageJacksonModule();
    }
}

最后，你可以使用Page对象了。

当然是测试：

@RunWith(SpringJUnit4ClassRunner.class)
@JsonTest
public class PageImplTest {

        @Autowired
        ObjectMapper mapper;

        @Test
        public  void page() throws IOException {
                String inputPageStr = "{\"content\":[{\"name\":\"n1\",\"gender\":\"boy\",\"age\":23},{\"name\":\"n2\",\"gender\":\"girl\",\"age\":20}],\"pageable\":\"INSTANCE\",\"totalPages\":1,\"last\":true,\"totalElements\":2,\"sort\":{\"sorted\":false,\"unsorted\":true,\"empty\":true},\"first\":true,\"numberOfElements\":2,\"size\":2,\"number\":0,\"empty\":false}";
                Page<PageItem> pageItems = mapper
                        .readValue(inputPageStr, new TypeReference<Page<PageItem>>() {});
                Assert.assertNotNull(pageItems);
        }

        static class PageItem {

                private String name;
                private String gender;
                private int age;

                public PageItem() {
                }

                public PageItem(String name, String gender, int age) {
                        this.name = name;
                        this.gender = gender;
                        this.age = age;
                }

                public String getName() {
                        return name;
                }

                public void setName(String name) {
                        this.name = name;
                }

                public String getGender() {
                        return gender;
                }

                public void setGender(String gender) {
                        this.gender = gender;
                }

                public int getAge() {
                        return age;
                }

                public void setAge(int age) {
                        this.age = age;
                }
        }

        @Configuration
        static class TestConfig{
                @Bean
                public Module pageJacksonModule() {
                        return new PageJacksonModule();
                }
        }
}

Answer 2

package com.td.support;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.JsonNode;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;

import java.util.ArrayList;
import java.util.List;

public class RestResponsePage<T> extends PageImpl<T> {
    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    public RestResponsePage(@JsonProperty("content") List<T> content,
                        @JsonProperty("number") int number,
                        @JsonProperty("size") int size,
                        @JsonProperty("totalElements") Long totalElements,
                        @JsonProperty("pageable") JsonNode pageable,
                        @JsonProperty("last") boolean last,
                        @JsonProperty("totalPages") int totalPages,
                        @JsonProperty("sort") JsonNode sort,
                        @JsonProperty("first") boolean first,
                        @JsonProperty("numberOfElements") int numberOfElements) {

        super(content, PageRequest.of(number, size), totalElements);
    }

    public RestResponsePage(List<T> content, Pageable pageable, long total) {
        super(content, pageable, total);
    }

    public RestResponsePage(List<T> content) {
        super(content);
    }

    public RestResponsePage() {
        super(new ArrayList<>());
    }
}

spring boot 2.0 上面可能没问题..