在数据库建立后，可以用Middlegen生成每个表对应的hbm.xml文件，并用hibernate-extensions生成对应的Java类。在后期开发时，如果要修改表，修改完后再走一遍这样的流程，那就显得有些繁琐。用XDoclet可以直接根据修改后的Java类生成对应的hbm.xml文件，这样可以减少维护的工作量。下面是我的一个简单例子。
我使用的数据库是MySQL 4.1.11，在数据库test中有这样一个用户表：
1
CREATE TABLE IF NOT EXISTS User
2(
3 Guid INT NOT NULL AUTO_INCREMENT,
4 Account VARCHAR(64) NOT NULL,
5 Password VARCHAR(16) NOT NULL,
6 Email VARCHAR(128) NOT NULL,
7 PRIMARY KEY (Guid)
8) TYPE=InnoDB; 根据该表写了一个User类，并且加上了XDoclet的tag。XDoclet有关hibernate的tag可以参考：
http://xdoclet.sourceforge.net/xdoclet/tags/hibernate-tags.html
1package sample.hibernate;
2
3import java.io.Serializable;
4
5
/**//**
6
* <p>Title: </p>
7 *
8 * <p>Description: </p>
9 *
10 * <p>Copyright: Copyright (c) 2005</p>
11 *
12 * <p>Company: </p>
13 *
14 * @author George Hill
15 * @version 1.0
16
*/
17
18/**//**
19 * @hibernate.class
20 * table="User"
21 * dynamic-update="true"
22 * dynamic-insert="true"
23 */
24public class User implements Serializable 
{
25
26 // identifier field
27 private int guid;
28
29 // persistent field
30 private String account;
31
32 // persistent field
33 private String password;
34
35 // persistent field
36 private String email;
37
38
/**//**
39 * default constructor
40
*/
41 public User() {}
42
43 /**//**
44 * full constructor
45 */
46 public User(String account, String password, String email) {
47 this.account = account;
48 this.password = password;
49 this.email = email;
50 }
51
52 /**//**
53 * @hibernate.id
54 * generator-class="native"
55 * type="int"
56 * column="Guid"
57 */
58 public int getGuid() {
59 return guid;
60 }
61
62 public void setGuid(int guid) {
63 this.guid = guid;
64 }
65
66 /**//**
67 * @hibernate.property
68 * column="Account"
69 * length="64"
70 * not-null="true"
71 */
72 public String getAccount() {
73 return account;
74 }
75
76 public void setAccount(String account) {
77 this.account = account;
78 }
79
80 /**//**
81 * @hibernate.property
82 * column="Password"
83 * length="16"
84 * not-null="true"
85 */
86 public String getPassword() {
87 return password;
88 }
89
90 public void setPassword(String password) {
91 this.password = password;
92 }
93
94 /**//**
95 * @hibernate.property
96 * column="Email"
97 * length="128"
98 * not-null="true"
99 */
100 public String getEmail() {
101 return email;
102 }
103
104 public void setEmail(String email) {
105 this.email = email;
106 }
107
108}
109 为了生成hbm.xml文件，需要用到ant，下面是我的build.xml文件的内容：
1<?xml version="1.0" encoding="ISO-8859-1"?>
2
3<project name="Hibernate XDoclet Examples" default="hibernate" basedir=".">
4 <property name="xdoclet.root.dir" value="D:/lib/xdoclet-1.2.3"/>
5 <property name="xdoclet.lib.dir" value="${xdoclet.root.dir}/lib"/>
6
7 <path id="sampleclasspath">
8 <fileset dir="${xdoclet.lib.dir}">
9 <include name="*.jar"/>
10 </fileset>
11 </path>
12
13 <taskdef
14 name="hibernatedoclet"
15 classname="xdoclet.modules.hibernate.HibernateDocletTask"
16 classpathref="sampleclasspath"
17 />
18
19 <target name="hibernate" description="Generate mapping documents">
20
21 <echo>+---------------------------------------------------+</echo>
22 <echo>| |</echo>
23 <echo>| R U N N I N G H I B E R N A T E D O C L E T |</echo>
24 <echo>| |</echo>
25 <echo>+---------------------------------------------------+</echo>
26
27 <hibernatedoclet
28 destdir="./src"
29 excludedtags="@version,@author,@todo,@see"
30 addedtags="@xdoclet-generated at ${TODAY},@copyright The XDoclet Team,@author XDoclet,@version ${version}"
31 force="false"
32 verbose="true">
33
34 <fileset dir="./src">
35 <include name="sample/hibernate/*.java"/>
36 </fileset>
37
38 <hibernate version="2.1"/>
39
40 </hibernatedoclet>
41 </target>
42</project>
43 build.xml文件中的第四行是指定XDoclet的根路径，需要根据解压的路径做相应的修改。XDoclet的下载地址：
http://xdoclet.sourceforge.net/xdoclet/install.html。在taskdef里面需要指定classname为xdoclet.modules.hibernate.HibernateDocletTask。在34行的fileset里面需要指定你的Java类所在的包路径。
运行ant，可以看到生成的User.hbm.xml文件的内容如下：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping
>
<class
name="sample.hibernate.User"
table="User"
dynamic-update="true"
dynamic-insert="true"
>
<id
name="guid"
column="Guid"
type="int"
>
<generator class="native">
<!--
To add non XDoclet generator parameters, create a file named
hibernate-generator-params-User.xml
containing the additional parameters and place it in your merge dir.
-->
</generator>
</id>
<property
name="account"
type="java.lang.String"
update="true"
insert="true"
column="Account"
length="64"
not-null="true"
/>
<property
name="password"
type="java.lang.String"
update="true"
insert="true"
column="Password"
length="16"
not-null="true"
/>
<property
name="email"
type="java.lang.String"
update="true"
insert="true"
column="Email"
length="128"
not-null="true"
/>
<!--
To add non XDoclet property mappings, create a file named
hibernate-properties-User.xml
containing the additional properties and place it in your merge dir.
-->
</class>
</hibernate-mapping>
posted on 2005-05-17 10:20
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