java - JAX-RS 中 ContextResolver 的用途

Question

我想了解 JAX-RS 中上下文解析器的用途。在什么情况下我应该实现上下文解析器？有人可以用一些例子详细说明吗？

我引用了 JAX-RS 2.0 规范并发现了以下段落:

Context providers supply context to resource classes and other providers. A context provider class implements the ContextResolver interface and may be annotated with @Provider for automatic discovery. E.g., an application wishing to provide a customized JAXBContext to the default JAXB entity providers would supply a class implementing ContextResolver.

我不知道何时何地使用。

Answer 1

我已经使用 ContextResolver 将驼峰式大小写转换为下划线(请参见下面的示例)，因此基本上您可以进行配置(就像文档所述)。

package com.example;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;

@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {

    private final ObjectMapper mapper;

    public ObjectMapperContextResolver() {
        mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(
                PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES
        );
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return mapper;
    }
}