java - Spring 将 JSON 映射到 java POJO

Question

我有 API 以这种格式返回 JSON:

[
    { "shrtName": "abc", "validFrom": "2016-10-23", "name": "aaa", "version": 1 },
    { "shrtName": "def", "validFrom": "2016-11-20", "name": "bbb", "version": 1 },
    { "shrtName": "ghi", "validFrom": "2016-11-22", "name": "ccc", "version": 1 }   
]

我有这段代码，它读取 API 并将其作为字符串返回。但我想读取这个 API 并将其映射到 Java POJO 类中。

public String downloadAPI(){
        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        headers.set("API-Key", "4444444-3333-2222-1111-88888888"); 
        HttpEntity<?> requestEntity = new HttpEntity<Object>(headers);
        String URL = "https://aaaaaaa.io/api/v1/aaaaaaaaa?date=2015-04-04;
        restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
        ResponseEntity<String> response = restTemplate.exchange(URL, HttpMethod.GET, requestEntity, String.class);
        return response.getBody();
}

我的问题:
1)POJO的格式？
2)我的方法的变化(返回类型POJO而不是String)

Answer 1

你的 JSON 是一个数组，这就是为什么 []

创建 POJO

public class MyPOJO {
    private String shrtName;
    private Date validFrom;
    private String name;
    private int version;    
}

删除消息转换器并将restTemplate交换方法重构为

ResponseEntity<MyPOJO[].class> response = restTemplate.exchange(URL, HttpMethod.GET, requestEntity, MyPOJO[].class);

这是我用于 GET 请求的通用函数

    public <T> T getRequestAndCheckStatus(final String url, final Class<T> returnTypeClass,
                                          final List<MediaType> mediaTypes,
                                          final Map<String, String> headerParams,
                                          final Map<String, Object> queryParams) throws Exception {

        final HttpHeaders headers = new HttpHeaders();
        headers.setAccept(mediaTypes);
        setHeaderParamsIfExists(headers, headerParams);
        final HttpEntity<String> requestEntity = new HttpEntity<>(headers);

        UriComponentsBuilder uriBuilder = UriComponentsBuilder.fromHttpUrl(url);
        setQueryParamsIfExists(uriBuilder, queryParams);

        final ResponseEntity<T> entity = restTemplate
                .exchange(getUrl(uriBuilder),
                          HttpMethod.GET,
                          requestEntity,
                          returnTypeClass);

        Assert.assertEquals(HttpStatus.OK, entity.getStatusCode());
        return entity.getBody();
    }

    private void setHeaderParamsIfExists(HttpHeaders headers, Map<String, String> headerParams) {
        if(headerParams != null && !headerParams.isEmpty())
            headerParams.entrySet()
                    .forEach(entry -> headers.set(entry.getKey(), entry.getValue()));
    }

    private void setQueryParamsIfExists(UriComponentsBuilder uriBuilder, Map<String, Object> queryParams) {
        if(queryParams != null && !queryParams.isEmpty())
            queryParams.entrySet()
                    .forEach(entry -> uriBuilder.queryParam(entry.getKey(), entry.getValue()));
    }

    private URI getUrl(UriComponentsBuilder uriBuilder) {
        return uriBuilder.build().encode().toUri();
    }

在您的情况下，您可以通过以下方式调用它

    getRequestAndCheckStatus("https://aaaaaaa.io/api/v1/aaaaaaaaa", MyPOJO[].class,                    
                             Collections.singletonList(MediaType.APPLICATION_JSON_UTF8), 
                             new HashMap<String, String>(){{ put("API-Key", "4444444-3333-2222-1111-88888888"); }}), 
                             new HashMap<String, Object>(){{ put("Date", "2015-04-04"); }});

• 此外，对于 Date，我建议使用 long，然后在 Controller 中将其解析为 Date。我看到您使用的是https协议(protocol)，您是否配置了证书？