错误：com.fasterxml.jackson.databind.JsonMappingException：未找到序列化程序

Question

我正在使用getQueryResults从bigquery作业中检索一个列表，并且（对我而言）它似乎转换为JSON失败。 我发现了这一点 ，并尝试了如下注释：

@JsonAutoDetect(fieldVisibility = Visibility.ANY)

虽然没有成功。

这是一段代码：

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.bigquery.Bigquery;
import com.google.api.services.bigquery.BigqueryScopes;
import com.google.api.services.bigquery.model.*;

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)

public class Query {
    private String id;
    private String sql;
    private List<TableRow> results;

    private static Bigquery createAuthorizedClient() throws IOException {
        HttpTransport transport = new NetHttpTransport();
        JsonFactory jsonFactory = new JacksonFactory();
        GoogleCredential credential = GoogleCredential.getApplicationDefault(transport, jsonFactory);
        // Depending on the environment that provides the default credentials (e.g. Compute Engine, App
        // Engine), the credentials may require us to specify the scopes we need explicitly.
        // Check for this case, and inject the Bigquery scope if required.
        if (credential.createScopedRequired()) {
            credential = credential.createScoped(BigqueryScopes.all());
        }

        return new Bigquery.Builder(transport, jsonFactory, credential).setApplicationName(" ...OMITTED... ").build();
    }

    public String getId() { return this.id;}
    public void setId(String id) { this.id = id; }

    public String getSql() { return this.sql; }
    public void setSql(String sql) { this.sql = sql;}

    public List<TableRow> getResults() { return this.results; }
    public void setResults(List<TableRow> r) { this.results = r; }

    public void update() {
        this.results = new ArrayList<TableRow>();
        if (!this.sql.isEmpty()){
            try {
                Bigquery bq = createAuthorizedClient();
                this.results = executeQuery(bq, this.sql);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private List<TableRow> executeQuery(Bigquery bq, String querySql) throws IOException {
        QueryResponse query = bq.jobs().query(" ...OMITTED... ", new QueryRequest().setQuery(querySql)).execute();

        // Execute it
        GetQueryResultsResponse queryResult = bq.jobs()
                .getQueryResults(query.getJobReference().getProjectId(), query.getJobReference().getJobId()).execute();

        List<TableRow> rows = queryResult.getRows();
        return rows;
    }

我不熟悉注释，也不知道如何将bigquery的回复转换为json，有人可以帮忙吗？

Answer 1

您必须自己构建JSON对象...

public void update() {
    String r = "{\"rows\": [";
    List<TableRow> bqresults;
    if (!this.sql.isEmpty()){
        try {
            Bigquery bq = createAuthorizedClient();
            bqresults = executeQuery(bq, this.sql);
            int rowIx = 0;
            int rowMax = bqresults.size() - 1;
            for(TableRow row : bqresults) {
                r += row.toString();
                rowIx++;
                if (rowIx <= rowMax) r += ",";
            }
            r += "]}";
            this.results = r;  
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}