dozer与BeanUtils

xiaoxiao2024-05-27 102

呵呵，在《develope J2EE without EJB》中，DTO被狠很地批判了一把，rod说这完全是反模式。可实际项目当中，我们还是不得不在使用。VO，PO，一牵扯到概念总是多么复杂。。。把一个PO从头传到尾？？从页面到数据库，一捅到底？NO，NO，万一你要显示给用户的是几个PO的结合怎么办？万一我们只是需要某几个属性组合在一起显示怎么办？一捅到底的策略是多么丑陋，而且你完全把你的数据库设计模型暴露给用户。所以我们需要一些map工具来转换，在这方面，过去我只知道有个 BeanUtils，不够灵活，而今天，接触了下dozer，啊，跟spring一样的理念！灵活多变，你想怎么映射，想怎么换都可以。看看它支持的转换类型：

• Primitive to Primitive Wrapper • Primitive to Custom Wrapper • Primitive Wrapper to Primitive Wrapper

• Primitive to Primitive • Complex Type to Complex Type • String to Primitive • String to Primitive Wrapper • String to Complex Type if the Complex Type contains a String constructor • Each of these can be mapped to one another: java.util.Date, java.sql.Date, java.sql.Time, java.sql.Timestamp, java.util.Calendar, java.util.GregorianCalendar • String to any of the supported Date/Calendar Objects if an explicit date format mapping attribute is specified. • Objects containing a toString() method that produces a long representing time in (ms) to any supported Date/Calendar object.

几乎我们能想到的，它都提供了方法来做到。而且dozer可以很容易地跟spring集成。下面举个简单例子：

定义一个Book对象：

package com.denny_blue.dozerdemo; public class Book { private String name; private String author; public Book(){ } public void setAuthor(String author) { this.author = author; }

public String getAuthor() { return (this.author); } public void setName(String name){ this.name=name; } public String getName(){ return this.name; } } 简单的，我们要实例化一个对象，然后clone此对象，注意，是clone！

package com.denny_blue.dozerdemo; import net.sf.dozer.util.mapping.DozerBeanMapper; import java.util.List; import java.util.ArrayList;

public class MyFirstDozerDemo { public static void main(String args[]){ Book book1=new Book(); book1.setAuthor("dennis"); book1.setName("dozer demo"); DozerBeanMapper mapper=new DozerBeanMapper(); Book book2=new Book(); mapper.map(book1,book2); book2=(Book)mapper.map(book1,com.denny_blue.dozerdemo.Book.class); System.out.println("book2's name:"+book2.getName()); } }

OK，如此简单，我们把book1的属性完全复制给了book2，两者现在是完全独立的对象。可如果仅仅是这样，我们用BeanUtils不是也很容易办到？ book2=(Book)BeanUtils.cloneBean(book1);可如果我要把book1映射给一个完全不同的类的对象怎么办？而且他们的属性名也不相同，怎么办？比如，一个CookBook类：

package com.denny_blue.dozerdemo; public class CookBook { private String bookName; private String author;

public CookBook(){} public String getBookName() { return (this.bookName); }

public void setBookName(String bookName) { this.bookName = bookName; }

public String getAuthor() { return (this.author); }

public void setAuthor(String author) { this.author = author; }

} 它的bookName属性与Book的name属性名不一样，我们该如何复制？dozer通过xml文件的配置来灵活地达到这个目的。我们配置一个dozerBeanMapping.xml：

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mappings PUBLIC "-//DOZER//DTD MAPPINGS//EN" "http://dozer.sourceforge.net/dtd/dozerbeanmapping.dtd"> <mappings> <configuration> <stop-on-errors>false</stop-on-errors> <date-format>MM/dd/yyyy HH:mm</date-format> <wildcard>true</wildcard> </configuration> <mapping> <class-a>com.denny_blue.dozerdemo.Book</class-a> <class-b>com.denny_blue.dozerdemo.CookBook</class-b> <field> <a>name</a> bookName </field> <field> <a>author</a> author </field> </mapping> </mappings>

如上所示，<class-a>指定所要复制的源对象，<class-b>复制的目标对象，<a>源对象的属性名， 目标对象的属性名。wildcard默认为true,在此时默认对所有属性进行map，如果为false，则只对在xml文件中配置的属性进行map。此时的demo 看起来像这样：

package com.denny_blue.dozerdemo; import net.sf.dozer.util.mapping.DozerBeanMapper; import java.util.List; import java.util.ArrayList;

public class MyFirstDozerDemo { public static void main(String args[]){ Book book1=new Book(); book1.setAuthor("dennis"); book1.setName("dozer demo"); DozerBeanMapper mapper=new DozerBeanMapper(); book2=(Book)mapper.map(book1,com.denny_blue.dozerdemo.Book.class); CookBook cookBook=new CookBook(); List myMappingFiles = new ArrayList(); myMappingFiles.add("dozerBeanMapping.xml"); mapper.setMappingFiles(myMappingFiles); cookBook=(CookBook)mapper.map(book1,CookBook.class); System.out.println("cookBook's name:"+ cookBook.getBookName()+" cookBook's author:"+ cookBook.getAuthor()); } }

通过mapper.setMappingFiles()设置映射文件，可以添加多个配置文件，也可以把所有的映射写在一个配置文件里面。更多复杂例子请见它自带的doc

文章转自庄周梦蝶，原文发布时间5.17