1

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

这是我用于初始化推土机的单例启动 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;
}
 }

它被注入的类是一个泛型类，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();
    }
}

它抛出一个空指针异常。我曾尝试将它用作无状态和有状态 bean，但结果保持不变。

任何帮助，将不胜感激。这是在 JBOSS AEP 6 上运行的 JAVA EE。

4

2 回答 2

1

事实证明，CDI 规范不允许将单例注入到泛型类型类中。所以我写了一个静态最终推土机实例的延迟初始化。

我在 DozerInstantiator 中添加了以下两种方法：

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");
    }
于 2013-11-08T09:40:14.730 回答
0

Dozer API 中包含一个单例/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。

于 2014-01-07T08:46:18.493 回答