如何通过标头在Apache Camel JPA中传递namedQuery参数? [英] how to pass namedQuery parameters in Apache Camel JPA by header?

问题描述

我有这条骆驼路线:

from("direct:getUser")
    .pollEnrich("jpa://User?namedQuery=User.findById&consumeDelete=false");

这是我的用户实体:

@Entity
@NamedQueries({
    @NamedQuery(name="User.findAll", query="SELECT u FROM User u"),
    @NamedQuery(name="User.findById", query="SELECT u FROM User u WHERE u.id = :id")
})
public class User{
    @Id
    private String id;
}

我通过设置标头尝试了此路线:

I have tried this route by setting the header:

from("direct:getUser")
    .setHeader("id", simple("myid"))
    .pollEnrich("jpa://User?namedQuery=User.findById&consumeDelete=false");

但是它不起作用

是否有任何方法可以通过标题设置jpa属性?骆驼文档在parameters选项中引用了此内容，但我没有找到示例

Is there any method to set jpa properties by the headers? The camel documentation quote this in parameters option but i don't found the examples

选项:parameters

此选项基于注册表，需要使用#表示法.这 键/值映射用于构建查询参数.它是 预期为通用类型java.util.Map，其中 键是给定JPA查询的命名参数及其值 是您要选择的相应有效值.骆驼 2.19:它也可以用于生产者.当用于生产者时，简单表达式可以用作参数值.它 允许您从邮件正文标头中检索参数值 等

This option is Registry based which requires the # notation. This key/value mapping is used for building the query parameters. It is expected to be of the generic type java.util.Map where the keys are the named parameters of a given JPA query and the values are their corresponding effective values you want to select for. Camel 2.19: it can be used for producer as well. When it's used for producer, Simple expression can be used as a parameter value. It allows you to retrieve parameter values from the message body header and etc.

推荐答案

我希望回答还不晚.无论如何，我的项目中都有类似的问题，客户端使用参数id进行HTTP GET，JPA查询使用该参数，最终将结果编组回HTTP客户端.我在Spring应用程序中运行骆驼.

I hope it's not too late to answer. In any case I had a similar issue in my project, the client does a HTTP GET with a parameter id, which is used by the JPA query and the result is finally marshalled back to the HTTP client. I'm running camel in a Spring application.

我终于想出了如何以一种合理的干净的方式来实现它.

I finally figured out how to achieve it in a reasonably clean way.

这是定义路径的RouteBuilder:

@Override
public void configure() throws Exception {

    Class dataClass = SomeClass.class;
    JacksonDataFormat format = new JacksonDataFormat();
    format.setUnmarshalType(dataClass);

    String jpaString = String
            .format("jpa://%1$s?resultClass=%1$s&namedQuery=q1" +
                    "&parameters={\"id\":${headers.id}}", dataClass.getName());

    from("jetty://http://localhost:8080/test").toD(jpaString) // note the .toD
        .marshal(format)
}

这是StringToMapTypeConverter类，否则骆驼无法将{"id":X}转换为地图

And this is the StringToMapTypeConverter class, otherwise camel cannot convert {"id": X} to a map

public class StringToMapTypeConverter implements TypeConverters {

    private static final ObjectMapper mapper = new ObjectMapper();
    private static JavaType mapType;

    static {
        mapType = mapper.getTypeFactory().constructMapType(Map.class,
                String.class, Object.class);
    }

    @Converter
    public Map<String, Object> toMap(String map) throws IOException {
        return mapper.readValue(map, mapType);
    }
}

请记住将其添加到上下文中.在春季，就像这样:

Remember to add it to the context. In Spring is something like:

<bean id="myStringToMapTypeConverter" class="....StringToMapTypeConverter" />

参考:

• http://camel.apache.org/jpa.html
• http://camel.apache.org/message-endpoint.html# MessageEndpoint-DynamicTo
• http://camel.apache.org/type-converter.html# TypeConverter-Addtypeconverterclassesatruntime

• http://camel.apache.org/jpa.html
• http://camel.apache.org/message-endpoint.html#MessageEndpoint-DynamicTo
• http://camel.apache.org/type-converter.html#TypeConverter-Addtypeconverterclassesatruntime

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