无法在 java 中创建 objectMapper

Question

我正在创建对象映射器的实例。

ObjectMapper objectMapper = new ObjectMapper();

这一行给我以下错误：

The constructor ObjectMapper() is undefined

我做错了什么？你能帮我么？提前致谢。

Answer 1

如果您使用 Jackson，您可能会缺少以下 jar

jackson-mapper-asl-1.5.0.jar

也尝试导入下面的包

import com.fasterxml.jackson.databind.*;

Answer 2

如果您使用 fasterxml jackson ObjectMapper，则构造函数为空：

/*
/**********************************************************
/* Life-cycle: constructing instance
/**********************************************************
 */

/**
 * Default constructor, which will construct the default
 * {@link JsonFactory} as necessary, use
 * {@link SerializerProvider} as its
 * {@link SerializerProvider}, and
 * {@link BeanSerializerFactory} as its
 * {@link SerializerFactory}.
 * This means that it
 * can serialize all standard JDK types, as well as regular
 * Java Beans (based on method names and Jackson-specific annotations),
 * but does not support JAXB annotations.
 */
public ObjectMapper() {
    this(null, null, null);
}

这是从 JavaDoc 复制的。请确保导入语句正确。我正在使用

import com.fasterxml.jackson.databind.ObjectMapper;

它对我有用。

Answer 3

检查您 class 中的库。

如果您错误地导入了同名的其他库，则会出现问题..

import org.elasticsearch.index.mapper.ObjectMapper;
import com.fasterxml.jackson.databind.*;

ObjectMapper objectMapper = new ObjectMapper();

在上面的例子中，第一行应该被删除。

无法在 java 中创建 objectMapper

can't create an objectMapper in java

java

jackson

objectmapper