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反序列化命名JSON数组[重复]

objectmapper deserialization json java

-1

Toseef Zafar · 技术社区 · 6 年前

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.annotate.JsonRootName;
import org.junit.Assert;
import org.junit.Test;

public class RootNodeTest extends Assert {

    @JsonRootName("customers")
    public static class Customer {
        public String email;
    }

    @Test
    public void testUnwrapping() throws IOException {
        String json = "{\"customers\":[{\"email\":\"hello@world.com\"},{\"email\":\"john.doe@example.com\"}]}";
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
        List<Customer> customers = Arrays.asList(mapper.readValue(json, Customer[].class));
        System.out.println(customers);
    }
}

我一直在翻阅杰克逊的文档,这是我能弄明白的,但在运行它时,我得到以下错误:

A org.codehaus.jackson.map.JsonMappingException has been caught, Root name 'customers' does not match expected ('Customer[]') for type [array type, component type: [simple type, class tests.RootNodeTest$Customer]] at [Source: java.io.StringReader@49921538; line: 1, column: 2]

我希望在不创建包装器类的情况下完成这项工作。虽然这是一个示例,但我不想创建不必要的包装类,只用于展开根节点。

0 回复 | 直到 10 年前

araqnid 10 年前

创建ObjectReader以显式配置根名称:

@Test
public void testUnwrapping() throws IOException {
    String json = "{\"customers\":[{\"email\":\"hello@world.com\"},{\"email\":\"john.doe@example.com\"}]}";
    ObjectReader objectReader = mapper.reader(new TypeReference<List<Customer>>() {})
                                      .withRootName("customers");
    List<Customer> customers = objectReader.readValue(json);
    assertThat(customers, contains(customer("hello@world.com"), customer("john.doe@example.com")));
}

(顺便说一句,这是杰克逊2.5,你有不同的版本吗?我有反序列化功能而不是DeserializationConfig.功能)

@JsonRootName 注释。

另外请注意,您可以直接请求 List<Customer> ObjectMapper.reader 就像第二个参数 ObjectMapper.readValue

-1

Community CDub 8 年前

根据 this @JsonRootName 注释只允许您展开包含pojo单个实例的json: "{\"customer\":{\"email\":\"hello@world.com\"}}";

-1

Arthur Eirich 10 年前

这个代码对我有用:

import org.codehaus.jackson.map.ObjectMapper;
import org.junit.Assert;
import org.junit.Test;

import java.io.IOException;
import java.util.List;

public class RootNodeTest extends Assert {

public static class CustomerMapping {
    public List<Customer> customer;

    public List<Customer> getCustomer() {
        return customer;
    }

    public static class Customer {
        public String email;

        public String getEmail() {
            return email;
        }
    }

}

@Test
public void testUnwrapping() throws IOException {
    String json = "{\"customer\":[{\"email\":\"hello@world.com\"},{\"email\":\"john.doe@example.com\"}]}";
    ObjectMapper mapper = new ObjectMapper();
    CustomerMapping customerMapping = mapper.readValue(json, CustomerMapping.class);
    List<CustomerMapping.Customer> customers = customerMapping.getCustomer();
    for (CustomerMapping.Customer customer : customers) {
        System.out.println(customer.getEmail());
    }
  }
}