那些遇到过的问题

带有分页API的Spring RestTemplate

tur*_*gos 35 rest spring resttemplate

我们的REST API在Pages中返回结果.以下是一个Controller的示例

@RequestMapping(value = "/search", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE + ";charset=UTF-8")
@ResponseStatus(HttpStatus.OK)
public Page<MyObject> findAll(Pageable pageable) {
  ...
}
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有没有一种简单的方法来使用RestTemplate使用该API？

如果我们这样做

ParameterizedTypeReference<Page<MyObject>> responseType = new ParameterizedTypeReference<Page<MyObject>>() { };

ResponseEntity<Page<MyObject>> result = restTemplate.exchange(url, HttpMethod.GET, null/*httpEntity*/, responseType);

List<MyObject> searchResult = result.getBody().getContent();
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它引发了一个例外 

org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not construct instance of org.springframework.data.domain.Page, 
problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information at [Source: java.io.PushbackInputStream@3be1e1f2; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of org.springframework.data.domain.Page, problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information
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先感谢您

小智 27

从Spring Boot 1.x迁移到2.0时,将读取Rest API响应的代码更改为

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 RestPageImpl<T> extends PageImpl<T>{

    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    public RestPageImpl(@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 RestPageImpl(List<T> content, Pageable pageable, long total) {
        super(content, pageable, total);
    }

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

    public RestPageImpl() {
        super(new ArrayList<>());
    }
}
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  • 这适用于除排序字段之外的所有内容，有没有人弄清楚如何反序列化和存储它？ (4认同)

tur*_*gos 14

将读取Rest API响应的代码更改为;

ParameterizedTypeReference<RestResponsePage<MyObject>> responseType = new ParameterizedTypeReference<RestResponsePage<MyObject>>() { };

ResponseEntity<RestResponsePage<MyObject>> result = restTemplate.exchange(url, HttpMethod.GET, null/*httpEntity*/, responseType);

List<MyObject> searchResult = result.getBody().getContent();
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这是我为RestResponsePage创建的类

package com.basf.gb.cube.seq.vaadinui.util;

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

import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;

public class RestResponsePage<T> extends PageImpl<T>{

  private static final long serialVersionUID = 3248189030448292002L;

  public RestResponsePage(List<T> content, Pageable pageable, long total) {
    super(content, pageable, total);
    // TODO Auto-generated constructor stub
  }

  public RestResponsePage(List<T> content) {
    super(content);
    // TODO Auto-generated constructor stub
  }

  /* PageImpl does not have an empty constructor and this was causing an issue for RestTemplate to cast the Rest API response
   * back to Page.
   */
  public RestResponsePage() {
    super(new ArrayList<T>());
  }

}
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Ste*_*hen 8

扩展上面,但不需要实现每个属性.

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
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 RestPageImpl<T> extends PageImpl<T>{

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

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

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

    public RestPageImpl() {
        super(new ArrayList());
    }
}
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  • 对于 Spring 2.3.3，我遇到编译错误：“new PageRequest(page, size)”具有受保护的访问权限。您可以使用“PageRequest.of(page, size)”。 (2认同)

Lor*_*ren 6

我不得不做一个小的改变，这样它就会忽略最近引入的空的未知属性。

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
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;

@JsonIgnoreProperties(ignoreUnknown = true)
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<>());
    }
}
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Vla*_*tev 5

没有必要实施Page. 您只需PagedResources<T>在您的ParameterizedTypeReference.

因此，如果您的服务返回类似于（为简洁起见删除对象）的响应：

{
    "_embedded": {
        "events": [
            {...},
            {...},
            {...},
            {...},
            {...}
        ]
    },
    "_links": {
        "first": {...},
         "self": {...},
         "next": {...},
         "last": {...}
    },
    "page": {
        "size": 5,
        "totalElements": 30,
        "totalPages": 6,
        "number": 0
    }
}
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并且您关心的对象是类型，Event那么您应该执行如下请求：

ResponseEntity<PagedResources<Event>> eventsResponse = restTemplate.exchange(uriBuilder.build(true).toUri(),
                HttpMethod.GET, null, new ParameterizedTypeReference<PagedResources<Event>>() {});
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如果您掌握了以下资源：

PagedResources<Event> eventsResources = eventsResponse.getBody();
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您将能够访问页面元数据（您在该"page"部分中获得的内容）、链接（"_links"部分）和内容：

Collection<Event> eventsCollection = eventsResources.getContent();
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Dan*_*dar 5

Kotlin 中的解决方案

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

class RestResponsePage<T> : PageImpl<T> {
    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    constructor(@JsonProperty("content") content: List<T>,
                @JsonProperty("number") number: Int,
                @JsonProperty("size") size: Int,
                @JsonProperty("totalElements") totalElements: Long?,
                @JsonProperty("pageable") pageable: JsonNode,
                @JsonProperty("last") last: Boolean,
                @JsonProperty("totalPages") totalPages: Int,
                @JsonProperty("sort") sort: JsonNode,
                @JsonProperty("first") first: Boolean,
                @JsonProperty("numberOfElements") numberOfElements: Int) : super(content, PageRequest.of(number, size), totalElements!!) {
    }

    constructor(content: List<T>, pageable: Pageable, total: Long) : super(content, pageable, total) {}

    constructor(content: List<T>) : super(content) {}

    constructor() : super(ArrayList<T>()) {}
}
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并要求

var response: ResponseEntity<*> = restTemplate.getForEntity<RestResponsePage<SomeObject>>(url)
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Java 中的解决方案

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<>());
    }
}
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如何使用Spring RestTemplate使用Page <Entity>响应 30
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