使用xsl来动态生成java代码

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）：

<?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：

<?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：

/**

* 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;

}

}