Struts（15）类型转换

在HTTP请求中的一切都被视为一个String由协议。这包括数字，布尔值，整数，日期，小数和一切。每一件事情是一个字符串，将根据HTTP。然而，Struts类可以有任何数据类型的属性。Struts的自动装配属性？

Struts使用了多种类型转换器在幕后做繁重。例如，如果Action类的属性有一个整数，Struts的自动转换请求参数的整数属性没有做任何事情。默认情况下，Struts的一些类型转换器。下面列出了他们中的一些，如果您正在使用其中任何一个，那么你有什么可担心的：

• Integer, Float, Double, Decimal

• Date and Datetime

• Arrays and Collections

• Enumerations

• Boolean

• BigDecimal

有些时候，当使用自己的数据类型，它是需要添加自己的转换，使Struts知道如何将这些值，然后显示。考虑以下POJO类Environment.java。

<span class="kwd" style="margin: 0px; padding: 0px;">package</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">class</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">private</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;">  </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">this</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">name </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> getName</span><span class="pun" style="margin: 0px; padding: 0px;">()</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">void</span><span class="pln" style="margin: 0px; padding: 0px;"> setName</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">this</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">name </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="pun" style="margin: 0px; padding: 0px;">}</span>

这是一个非常简单的类，它有一个名为name的属性，所以没有什么特别的关于这个类。我们创建包含有关系统 - SystemDetails.java信息另一个类。目的是练习，我有硬编码环境，以“开发”在操作系统“Windows XP SP3”。在实际项目中，会从系统配置得到信息。因此，让我们有以下动作类： 

<span class="kwd" style="margin: 0px; padding: 0px;">package</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">import</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">opensymphony</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">xwork2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">ActionSupport</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">class</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">SystemDetails</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">extends</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">ActionSupport</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">private</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> environment </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">new</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="str" style="margin: 0px; padding: 0px;">"Development"</span><span class="pun" style="margin: 0px; padding: 0px;">);</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">private</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> operatingSystem </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="str" style="margin: 0px; padding: 0px;">"Windows XP SP3"</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> execute</span><span class="pun" style="margin: 0px; padding: 0px;">()</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> SUCCESS</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> getEnvironment</span><span class="pun" style="margin: 0px; padding: 0px;">()</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> environment</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">void</span><span class="pln" style="margin: 0px; padding: 0px;"> setEnvironment</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> environment</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">this</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">environment </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> environment</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> getOperatingSystem</span><span class="pun" style="margin: 0px; padding: 0px;">()</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> operatingSystem</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">void</span><span class="pln" style="margin: 0px; padding: 0px;"> setOperatingSystem</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> operatingSystem</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">this</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">operatingSystem </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> operatingSystem</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="pun" style="margin: 0px; padding: 0px;">}</span>

接下来让我们创建一个简单的JSP文件System.jsp显示环境和操作系统信息。

<span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> page language</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"java"</span><span class="pln" style="margin: 0px; padding: 0px;"> contentType</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"text/html; charset=ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">pageEncoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">%></span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> taglib prefix</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"s"</span><span class="pln" style="margin: 0px; padding: 0px;"> uri</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"/struts-tags"</span><span class="pln" style="margin: 0px; padding: 0px;">%></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><html></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><title></span><span class="pln" style="margin: 0px; padding: 0px;">System Details</span><span class="tag" style="margin: 0px; padding: 0px;"></title></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><body></span><span class="pln" style="margin: 0px; padding: 0px;">   Environment: </span><span class="tag" style="margin: 0px; padding: 0px;"><s:property</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"environment"</span><span class="tag" style="margin: 0px; padding: 0px;">/><br/></span><span class="pln" style="margin: 0px; padding: 0px;">   Operating System:</span><span class="tag" style="margin: 0px; padding: 0px;"><s:property</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"operatingSystem"</span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></body></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></html></span>

让我们编写 system.jsp，SystemDetails.java类在struts.xml一起使用。 SystemDetails类有一个简单的execute（）方法返回字符串“SUCCESS”。

<span class="pun" style="margin: 0px; padding: 0px;"><?</span><span class="pln" style="margin: 0px; padding: 0px;">xml version</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"1.0"</span><span class="pln" style="margin: 0px; padding: 0px;"> encoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"UTF-8"</span><span class="pun" style="margin: 0px; padding: 0px;">?></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE struts PUBLIC    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"    "http://struts.apache.org/dtds/struts-2.0.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><struts></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><constant</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts.devMode"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"true"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><package</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"helloworld"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">extends</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts-default"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><action</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"system"</span><span class="pln" style="margin: 0px; padding: 0px;">             </span><span class="atn" style="margin: 0px; padding: 0px;">class</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"com.yiibai.struts2.SystemDetails"</span><span class="pln" style="margin: 0px; padding: 0px;">             </span><span class="atn" style="margin: 0px; padding: 0px;">method</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"execute"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"success"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/System.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"></action></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"></package></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></struts></span>

右键点击项目名称，并单击 Export > WAR File 创建一个WAR文件。然后部署此WAR在Tomcat的webapps目录下。最后，启动Tomcat服务器和尝试访问URL http://localhost:8080/HelloWorldStruts2/system.action。这会给出以下画面：

上面的输出有什么错？ Struts 知道如何显示字符串“Windows XP SP3”等内置数据类型转换，但它不知道用Environmenttype属性做什么。所以，它只是被称为类的toString（）方法。为了解决这个问题，现在让我们创建并注册一个简单的TypeConverter环境类。创建一个类名为EnvironmentConverter.java以下。

<span class="kwd" style="margin: 0px; padding: 0px;">package</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">import</span><span class="pln" style="margin: 0px; padding: 0px;"> java</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">util</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">Map</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">import</span><span class="pln" style="margin: 0px; padding: 0px;"> org</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">apache</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">util</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">StrutsTypeConverter</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">class</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">EnvironmentConverter</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">extends</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">StrutsTypeConverter</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="lit" style="margin: 0px; padding: 0px;">@Override</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Object</span><span class="pln" style="margin: 0px; padding: 0px;"> convertFromString</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">Map</span><span class="pln" style="margin: 0px; padding: 0px;"> context</span><span class="pun" style="margin: 0px; padding: 0px;">,</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pun" style="margin: 0px; padding: 0px;">[]</span><span class="pln" style="margin: 0px; padding: 0px;"> values</span><span class="pun" style="margin: 0px; padding: 0px;">,</span><span class="pln" style="margin: 0px; padding: 0px;">                                       </span><span class="typ" style="margin: 0px; padding: 0px;">Class</span><span class="pln" style="margin: 0px; padding: 0px;"> clazz</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> env </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">new</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="pln" style="margin: 0px; padding: 0px;">values</span><span class="pun" style="margin: 0px; padding: 0px;">[</span><span class="lit" style="margin: 0px; padding: 0px;">0</span><span class="pun" style="margin: 0px; padding: 0px;">]);</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> env</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="lit" style="margin: 0px; padding: 0px;">@Override</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> convertToString</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">Map</span><span class="pln" style="margin: 0px; padding: 0px;"> context</span><span class="pun" style="margin: 0px; padding: 0px;">,</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">Object</span><span class="pln" style="margin: 0px; padding: 0px;"> value</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> env  </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> value</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> env </span><span class="pun" style="margin: 0px; padding: 0px;">==</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">null</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">?</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">null</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">:</span><span class="pln" style="margin: 0px; padding: 0px;"> env</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">getName</span><span class="pun" style="margin: 0px; padding: 0px;">();</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="pun" style="margin: 0px; padding: 0px;">}</span>

EnvironmentConverter 扩展了 StrutsTypeConverter 类，如何将环境为一个 String，反之亦然通过重写两个的方法 convertFromString（）和 convertToString（）并通知了Struts。现在，让我们注册这个转换器之前，我们我们在我们的应用程序。有两种方法来注册一个转换器。如果转换器将只用于在一个特定的动作，那么将需要创建一个属性文件需要被命名为 '[action-class]'-converstion.properties，所以，在我们的例子中，我们创建一个名为SystemDetails下面的注册 converstion.properties 输入： 

<span class="pln" style="margin: 0px; padding: 0px;">environment</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;">com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">EnvironmentConverter</span>

在上面的例子中，“environment”的名字是在SystemDetails.java 类的一个属性，告诉要使用Struts EnvironmentConverter从这个属性的转换。但是，我们不打算这样做，相反，我们要在全局范围内注册这个转换器，因此，它可以在整个应用程序。要做到这一点，创建一个属性文件名为 xwork-conversion.properties 在 WEB-INF/classes文件夹下面一行：

<span class="pln" style="margin: 0px; padding: 0px;">com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">Environment</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> \            com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">EnvironmentConverter</span>

这简单的注册全局转换器，这样的Struts可以自动做转换每次遇到一个对象类型的环境。现在，如果重新编译并重新运行该程序，会得到更好的输出如下：

很显然，现在的结果是更好的，这意味着我们的Struts的转换工作正常。这是可以创建多个转换器和按要求注册后才能使用。