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运用xsl来动态生成java代码

技术开发2024-06-10 阅读()
xsl本身就是一个构型良好的xml,它能够把一个xml文档转换成另外一个xml文档,或者转换成文本文件、html文件等等。这里就是利用xsl来动态的生成我们想要的java文件(从某种角度看,java代码其实也就是一个文本文件),希望能够通过这篇文章,看到xml以及相关的技术所具有的强大能力!

这里首先给一个xml例子,我们将通过一个xsl从该xml文件中抽取有用的信息来生成java代码(实际上是一个javabean):
以下内容为程序代码:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<bean>
<name>Product</name>
<comments>This bean represents a product that the company
offers to its customers</comments>
<property>
<name>code</name>
<type>int</type>
<comments>the product inventory code</comments>
</property>
<property>
<name>name</name>
<type>String</type>
<comments>the product name</comments>
</property>
<property>
<name>testedOnAnimals</name>
<type>boolean</type>
<comments>the flag that indicates if the product was
tested on animals</comments>
</property>
<property>
<name>availableSince</name>
<type>java.util.Date</type>
<comments>the date when the company started offering this
product to its customers</comments>
</property>
</bean>


下面我就直接给出转换的xsl,如果大家对xsl不是很了解的话,可以先看一些资料,了解之后就会明白了。我在里面稍微做了些注释:
以下内容为程序代码:

<?xml version="1.0"?>
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0" 
xmlns:java="http://xml.apache.org/xslt/java"
exclude-result-prefixes="java">

<!--这里就是指定通过这个xsl所转换的结果的类型,是text格式-->
<xsl:output method = "text"/>

<!--xslt使用模版来处理xml中的节点-->
<xsl:template match="bean">

/**
* <xsl:value-of select="comments"/>//这里是获取xml文档中的节点值
* This class has been generated by the XSLT processor from the
metadata
*/
public class <xsl:value-of select="name"/> {

/**
 * Creates a new instance of the <xsl:value-of
select="name"/> bean
 */
public <xsl:value-of select="name"/>() {}
 
<xsl:apply-templates select="property"/>
}
</xsl:template>

<xsl:template match="property">
private <xsl:value-of select="type"/>
<xsl:text> </xsl:text>//输出文本,这里是输出一个空格
<xsl:value-of select="name"/>;
<xsl:variable name="name" select="name"/>//定义xsl中要使用的变量
<xsl:variable name="cname" select="java:Capitalizer.capitalize($name)"/>//这里使用了xslt extensions,它可以允许在xslt中直接引用java中方法,非常方便。
/**
 * Sets <xsl:value-of select="comments"/>
 * @param <xsl:value-of select="name"/> is <xsl:value-of
select="comments"/>
 */
public void set<xsl:value-of select="$cname"/>(<xsl:value-
of select="type"/> <xsl:text> </xsl:text><xsl:value-
of select="name"/>) {
this.<xsl:value-of select="name"/> = <xsl:value-of
select="name"/>;
}

/**
 * Returns <xsl:value-of select="comments"/>
 * @return <xsl:value-of select="comments"/>
 */
public <xsl:value-of select="type"/><xsl:text></xsl:text>
<xsl:apply-templates select="type"/><xsl:value-of
select="$cname"/>() {
return <xsl:value-of select="name"/>;
}
</xsl:template>

<xsl:template match="type">
<xsl:variable name="type" select="."/>
<xsl:choose>
<xsl:when test="$type='boolean'">is</xsl:when>
<xsl:otherwise>get</xsl:otherwise>
</xsl:choose>
</xsl:template>

</xsl:stylesheet>


好了,完成以上工作之后,只要在cmd中,输入如下的命令行,就可以获得我们想要的结果了:
java org.apache.xalan.xslt.Process -in xmlSource-xsl stylesheet -out outputfile

这里列出结果:
以下内容为程序代码:

/**
* This bean represents a product that the company offers to its
customers
* This class has been generated by the XSLT processor from the
metadata
*/
public class Product {

/**
 * Creates a new instance of the Product bean
 */
public Product() {}
 
 
private int code;
 
/**
 * Sets the product inventory code
 * @param code is the product inventory code
 */
public void setCode(int code) {
this.code = code;
}

/**
 * Returns the product inventory code
 * @return the product inventory code
 */
public int getCode() {
return code;
}

private String name;
 
/**
 * Sets the product name
 * @param name is the product name
 */
public void setName(String name) {
this.name = name;
}

/**
 * Returns the product name
 * @return the product name
 */
public String getName() {
return name;
}

private boolean testedOnAnimals;
 
/**
* Sets the flag that indicates if the product was tested on animals
* @param testedOnAnimals is the flag that indicates if the product
was tested on animals
*/
public void setTestedOnAnimals(boolean testedOnAnimals) {
this.testedOnAnimals = testedOnAnimals;
}

/**
 * Returns the flag that indicates if the product was tested on
animals
 * @return the flag that indicates if the product was tested on
animals
 */
public boolean isTestedOnAnimals() {
return testedOnAnimals;
}

private java.util.Date availableSince;
 
/**
 * Sets the date when the company started offering this product to
its customers
 * @param availableSince is the date when the company started
offering this product to its customers
 */
public void setAvailableSince(java.util.Date availableSince) {
this.availableSince = availableSince;
}

/**
 * Returns the date when the company started offering this product
to its customers
 * @return the date when the company started offering this product
to its customers
 */
public java.util.Date getAvailableSince() {
return availableSince;
}

}


总结:
1. 在熟悉了xsl的基本使用之后,理解以上的内容并不是困难;
2. 这样做是比较适合预先知道了某些逻辑功能,但由于某种原因,需要动态生成,或者是为了节省不必要的重复工作,可以通过它自动生成代码;
3. 修改这个xsl比较方便。

sjoy

……

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