Question

我为Dozer创建了一个instatiator bean（http://dozer.sourceforge.net/）。但是当我注入这个EJB时，它会抛出nullpointer异常。

这是我用于初学Dozer的Singleton启动Bean

package com.unijunction.ordercloud.common.rest;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.inject.Singleton;
import javax.ejb.Startup;

import org.dozer.DozerBeanMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@Startup
@Singleton
public class DozerInstantiator {

private DozerBeanMapper mapper;

private Logger log = LoggerFactory.getLogger(DozerInstantiator.class);

public enum States {
    BEFORESTARTED, STARTED, PAUSED, SHUTTINGDOWN
};

private States state;

//TODO: DozerIsntantiator is retunring null

@PostConstruct
public void initialize() throws Throwable {
    log.info("---------------Dozer  Starting Up-----------------");
    try{
        state = States.BEFORESTARTED;
        this.mapper = new DozerBeanMapper();

     } catch (Throwable e) {
            log.error("Cause: " + e.getCause());
            log.error("Message: " + e.getMessage());
            log.error("Class: " + e.getClass());
            log.error("StackTrace: " + e.getStackTrace());
            throw e;
        }

    state = States.STARTED;
    log.info("---------------Dozer  Started-----------------");
}


@PreDestroy
public void terminate() {
    state = States.SHUTTINGDOWN;
    // Perform termination
    log.info("---------------Dozer  Shuttingdown-----------------");
}

public States getState() {
    return this.state;
}

public void setState(States state) {
    this.state = state;
}

public DozerBeanMapper getMapper() {
    return this.mapper;
}
 }

它被注入的类是泛型类，如下所示：

public class DtoConverter<T1, T>  {

protected final Class<T> entityClass;

@EJB
DozerInstantiator dozerInstantiator;

//instance for dozer to convert beans
protected DozerBeanMapper mapper;

private Logger log = LoggerFactory.getLogger(DozerInstantiator.class);

public DtoConverter(){
    this.entityClass = null;
}

/**
 * Setup the class
 *
 */
public DtoConverter(Class<T> entityClass) {
    this.entityClass = entityClass;
    //TODO: only allow one instance of this to exist
    //https://ordercloud.atlassian.net/browse/API-80
    try{
        mapper = dozerInstantiator.getMapper(); //<--- This throws null pointer
    }catch(Exception e){
        mapper = new DozerBeanMapper();
    }
}

抛出空指针异常。我已经尝试将它用作Stateless和Statefull bean，但结果仍然相同。

任何帮助将不胜感激。这是在JBOSS AEP 6上运行的JAVA EE。

Answer 1

事实证明，CDI规范不允许将单例注入到泛型类中。所以我写了一个静态的最终推土机实例的懒惰初始化。

我在DozerInstantiator中添加了以下两个方法：

public static DozerBeanMapper getInstance(){
    return MapperHolder.instance;
}

private static class MapperHolder{
    static final DozerBeanMapper instance = new DozerBeanMapper(mappingList);
}

然后在泛型类中调用它：

DozerInstantiator dozerInstantiator = new DozerInstantiator();

    try{
        mapper = dozerInstantiator.getInstance();
    }catch(Exception e){
        log.error("Failed to initialise singleton Dozer bean");
    }

Answer 2

Dozer API中包含单身人士/此方法应符合您的需求

Mapper getMapper() {
        return DozerBeanMapperSingletonWrapper.getInstance();
    }

如果要将其转换为CDI，请参阅@Produce注释规范。

Dozer Singleton Startup Bean被称为Null

2 个答案: