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我正在尝试获取价格大于某个值但无法正确使用过滤器表达式的所有商品。

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Region;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.ItemCollection;
import com.amazonaws.services.dynamodbv2.document.QueryOutcome;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.spec.QuerySpec;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.PutItemRequest;
import com.amazonaws.services.dynamodbv2.model.ScanRequest;
import com.amazonaws.services.dynamodbv2.model.ScanResult;

public class QuerySample {
    // Setting up the client

    static AmazonDynamoDBClient db = new AmazonDynamoDBClient(
            new ProfileCredentialsProvider());
    // Setting up the DB
    static DynamoDB dynamoDB = new DynamoDB(db);

    public static void main(String a[]) {
        // Setting up the Region
        Region usWest = Region.getRegion(Regions.US_WEST_2);
        db.setRegion(usWest);
        Table table = dynamoDB.getTable("Thread");
        SimpleDateFormat dt = new SimpleDateFormat("yyyy-mm-dd HH:mm:ss.SSS");
        long time = (new Date()).getTime();
        Date date = new Date();
        date.setTime(time);
        System.out.println("The date is " + date);
        // ScanRequest scanRequest = new ScanRequest()
        // .withTableName("sys_ping");
        // ScanResult result = db.scan(scanRequest);
        // for (Map<String, AttributeValue> item : result.getItems()){
        // System.out.println(item);
        // }

        Map<String, Object> expressionAttributeValues = new HashMap<String, Object>();
        expressionAttributeValues.put(":val", "19");
        expressionAttributeValues.put(":val1",
                new AttributeValue().withN("2000"));
        ScanRequest scanRequest = new ScanRequest().withTableName(
                "ProductCatalog").withFilterExpression("Price >= :val");
        ScanResult result = db.scan(scanRequest);
        for (Map<String, AttributeValue> item : result.getItems()) {
            System.out.println(item);

        }

    }
}

它抛出以下运行时异常

线程“main”com.amazonaws.AmazonServiceException 中的异常：无效的FilterExpression：未定义表达式中使用的表达式属性值；属性值：：val（服务：AmazonDynamoDBv2；状态代码：400；错误代码：ValidationException；请求 ID：FEQBP55SPJIT60JVFPVO6N6BLBVV4KQNSO5AEMVJF66Q9ASUAAJG）

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2 回答 2

1

您在滥用 API。看着Map<String, Object> expressionAttributeValues

  1. 两者:val都有:val1。
  2. 您没有将其传递给new ScanRequest()
于 2015-02-05T17:26:29.263 回答
0

这是 DynamoDB API V2 的 Java 示例。假设我们有一个名为 Work 的表和一个名为 Archive 的列。存档列可以是关闭的或打开的。

在此处输入图像描述

现在假设，我们只想查询 Open 项目。使用 Java v2 和增强型客户端，我们可以按如下方式执行此查询。

package com.example.dynamodb;

// snippet-start:[dynamodb.java2.mapping.scanEx.import]
import java.time.Instant;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbTable;
import software.amazon.awssdk.enhanced.dynamodb.Expression;
import software.amazon.awssdk.enhanced.dynamodb.TableSchema;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSortKey;
import software.amazon.awssdk.enhanced.dynamodb.model.ScanEnhancedRequest;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
// snippet-end:[dynamodb.java2.mapping.scanEx.import]

/*
    This code example uses an Expression object to select only Open items for the archive column.
    Prior to running this code example, create a Work table that contains the following fields:

    1.  id - Represents the key.
    2. date - Specifies the date the item was created.
    3. description - A value that describes the item.
    4. guide - A value that represents the deliverable being worked on.
    5. status - A value that describes the status.
    6. username - A value that represents the user who entered the item.
    7. archive - A value that represents whether this is an active or archive item. Specify Open and Closed items.
 */

public class EnhancedScanRecordsWithExpression {
    // Query the Record table
    public static void main(String[] args) {

        //Create a DynamoDbClient object
        Region region = Region.US_EAST_1;
        DynamoDbClient ddb = DynamoDbClient.builder()
                .region(region)
                .build();
        // Create a DynamoDbEnhancedClient and use the DynamoDbClient object
        DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
                .dynamoDbClient(ddb)
                .build();

        scan(enhancedClient);
    }

    // snippet-start:[dynamodb.java2.mapping.scanEx.main]
    public static void scan(DynamoDbEnhancedClient enhancedClient) {

        try {
            //Create a DynamoDbTable object
            DynamoDbTable<Work> table = enhancedClient.table("Work", TableSchema.fromBean(Work.class));

            AttributeValue attr = AttributeValue.builder()
                    .s("Open")
                    .build();

            // Get only Open items in the Work table
            Map<String, AttributeValue> myMap = new HashMap<>();
            myMap.put(":val1", attr);

            Map<String, String> myExMap = new HashMap<>();
            myExMap.put("#archive", "archive");

            // Set the Expression so only Closed items are queried from the Work table
            Expression expression = Expression.builder()
                    .expressionValues(myMap)
                    .expressionNames(myExMap)
                    .expression("#archive = :val1")
                    .build();

            ScanEnhancedRequest enhancedRequest = ScanEnhancedRequest.builder()
                    .filterExpression(expression)
                    .limit(15)
                    .build();

            // Get items in the Record table and write out the ID value
            Iterator<Work> results = table.scan().items().iterator();

            while (results.hasNext()) {

                Work rec = results.next();
                System.out.println("The record id is " + rec.getId());
            }

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        System.out.println("Done");
    }
    // snippet-end:[dynamodb.java2.mapping.scanEx.main]
}
于 2020-09-23T18:44:01.227 回答