無法將“java.lang.String”類型的值轉換為所需類型

Question

我在 Spring-boot 2.2.1 上有 REST 服務器，使用 Spring-web 5.2.3 與 mysql 和 JavaFX 客戶端連接。 我想從客戶端向服務器發送 http 請求。 對於方法 GET 效果很好，但對於 POST 效果不佳。

我的實體：

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Entity(name = "CANDIDATES")
public class Candidate {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String lastname;

    @Enumerated(EnumType.STRING)
    private Education education;

    private String placeOfResidence;

    @ManyToMany(cascade = CascadeType.PERSIST)
    @JoinTable(
            name = "JOIN_VOTERESULTS_CANDIDATES",
            joinColumns = {@JoinColumn(name = "CANDIDATES_ID", referencedColumnName = "ID")},
            inverseJoinColumns = {@JoinColumn(name = "VOTERESULTS_ID",referencedColumnName = "ID")}
    )
    private List<VoteResult> voteResults;

    @ManyToOne
    @JoinColumn(name = "ELECTION_LISTS_ID")
    private ElectionList electionList;

    @ManyToOne
    @JoinColumn(name = "ELECTORAL_PARTIES_ID")
    private ElectoralParty electoralParty;
} 

CandidateDto 具有相同的變量。 這是我的 POST 控制器：

@PostMapping(value = "/createCandidate")
public void createCandidate(@Valid CandidateDto candidateDto) {
    service.createCandidate(candidateDto);
}

這是在客戶端創建此對象並將帶有正文的 POST 請求發送到服務器的方法：

RestTemplate restTemplate = new RestTemplate();

restTemplate.setMessageConverters(getMessageConverters());

URI url = UriComponentsBuilder.fromHttpUrl(URL + "/createCandidate")
    .queryParam("id", candidate.getId())
    .queryParam("name", candidate.getName())
    .queryParam("lastname", candidate.getLastname())
    .queryParam("education", candidate.getEducation())
    .queryParam("placeOfResidence", candidate.getPlaceOfResidence())
    .queryParam("voteResults", candidate.getVoteResults())
    .queryParam("electionList", candidate.getElectionList())
    .queryParam("electoralParty", candidate.getElectoralParty()).build().encode().toUri();

restTemplate.postForObject(url, null, Candidate.class);

當我刪除帶有選舉黨、選舉列表和投票結果的 queryParams 時，一切都很好。但是有了這些參數，我在服務器中出現了錯誤：

Field error in object 'candidateDto' on field 'education': rejected value [zawodowe]; codes [typeMismatch.candidateDto.education,typeMismatch.education,typeMismatch.com.pk.electionappserver.domain.Education,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [candidateDto.education,education]; arguments []; default message [education]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.Education' for property 'education'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [com.pk.electionappserver.domain.Education] for value 'zawodowe'; nested exception is java.lang.IllegalArgumentException: No enum constant com.pk.electionappserver.domain.Education.zawodowe]
Field error in object 'candidateDto' on field 'electionList': rejected value []; codes [typeMismatch.candidateDto.electionList,typeMismatch.electionList,typeMismatch.com.pk.electionappserver.domain.dto.ElectionListDto,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [candidateDto.electionList,electionList]; arguments []; default message [electionList]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.dto.ElectionListDto' for property 'electionList'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.dto.ElectionListDto' for property 'electionList': no matching editors or conversion strategy found]
Field error in object 'candidateDto' on field 'electoralParty': rejected value []; codes [typeMismatch.candidateDto.electoralParty,typeMismatch.electoralParty,typeMismatch.com.pk.electionappserver.domain.dto.ElectoralPartyDto,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [candidateDto.electoralParty,electoralParty]; arguments []; default message [electoralParty]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.dto.ElectoralPartyDto' for property 'electoralParty'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.dto.ElectoralPartyDto' for property 'electoralParty': no matching editors or conversion strategy found]
Field error in object 'candidateDto' on field 'voteResults': rejected value []; codes [typeMismatch.candidateDto.voteResults,typeMismatch.voteResults,typeMismatch.java.util.List,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [candidateDto.voteResults,voteResults]; arguments []; default message [voteResults]]; default message [Failed to convert property value of type 'java.lang.String' to required type 'java.util.List' for property 'voteResults'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'com.pk.electionappserver.domain.dto.VoteResultDto' for property 'voteResults[0]': no matching editors or conversion strategy found]]

和客戶端錯誤：

Caused by: org.springframework.web.client.HttpClientErrorException$BadRequest: 400 : [{"timestamp":"2020-01-17T16:17:45.333+0000","status":400,"error":"Bad Request","errors":[{"codes":["typeMismatch.candidateDto.education","typeMismatch.education","typeMismatch.com.pk.electionappserver... (3565 bytes)]
    at org.springframework.web.client.HttpClientErrorException.create(HttpClientErrorException.java:101)
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:170)
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:112)
    at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63)
    at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:785)
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:743)
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:717)
    at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:443)
    at com.pk.electionappclient.Controller.ClientController.createCandidate(ClientController.java:36)
    at com.pk.electionappclient.Controller.ClientController.addCandidate(ClientController.java:84)
    at com.pk.electionappclient.Controller.admin.NewCandidateController.createNewCandidate(NewCandidateController.java:116)

投票結果實體：

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Entity(name = "VoteResults")
public class VoteResult {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "USERS_ID")
    private User user;

    @ManyToOne
    @JoinColumn(name = "ELECTIONS_ID")
    private Election election;

    @ManyToMany(cascade = CascadeType.PERSIST)
    @JoinTable(
            name = "JOIN_VOTERESULTS_CANDIDATES",
            joinColumns = {@JoinColumn(name = "VOTERESULTS_ID",referencedColumnName = "ID")},
            inverseJoinColumns = {@JoinColumn(name = "CANDIDATES_ID", referencedColumnName = "ID")}
    )
    private List<Candidate> candidates;

    private LocalDateTime voteTime;
}

選舉列表實體：

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Entity(name = "ELECTION_LISTS")
public class ElectionList {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String description;

    @ManyToOne
    @JoinColumn(name = "ELECTION_ID")
    private Election election;

    @ManyToOne
    @JoinColumn(name = "CONSTITUENCY_ID")
    private Constituency constituency;

    @OneToMany(
            targetEntity = Candidate.class,
            mappedBy = "electionList",
            cascade = CascadeType.PERSIST,
            fetch = FetchType.LAZY
    )
    private List<Candidate> candidates;
}

選舉黨實體：

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Entity(name = "ELECTORAL_PARTIES")
public class ElectoralParty {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String description;

    @OneToMany(
            targetEntity = Candidate.class,
            mappedBy = "electoralParty",
            cascade = CascadeType.PERSIST,
            fetch = FetchType.LAZY
    )
    private List<Candidate> candidates;

    @OneToOne(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)
    @JoinColumn(name = "ELECTORAL_PROGRAMMES_ID")
    private ElectoralProgramme electoralProgramme;
}

Answer 1

1. 使用@Valid 添加@RequestBody
2. 查詢參數將不起作用，因為它會將值作為字符串傳遞，這就是您遇到強制轉換錯誤的原因。 這會將對象作為 object@137462 傳遞。 看看這個https://stackoverflow.com/a/36021268/4367186