今天我们将研究jaxb2-maven-plugin XJC的例子来生成Java类从XSD。JAXB是Java类和XML之间的中间软件技术,我们可以使用JAXB从Java对象生成XML,反之亦然。
jaxb2-maven 插件
我们使用 XSD 来定义合同数据结构,所以不常生成代表 XML 方案的 java 类. jaxb2-maven-plugin XJC 是 JAXB 绑定编译工具,可以用来从 XSD 文件生成 Java 类. 在这里,我们将学习如何在 maven 项目中使用 jaxb2-maven-plugin XJC 来生成 Java 类。
1<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
2 <modelVersion>4.0.0</modelVersion>
3 <groupId>jd</groupId>
4 <artifactId>jd</artifactId>
5 <version>0.0.1-SNAPSHOT</version>
6
7 <name>JD Example XSD to Java</name>
8
9 <properties>
10 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
11 </properties>
12 <build>
13 <plugins>
14 <!-- Plugin required to build java classes from XSD using XJC -->
15 <plugin>
16 <groupId>org.codehaus.mojo</groupId>
17 <artifactId>jaxb2-maven-plugin</artifactId>
18 <version>1.5</version>
19 <executions>
20 <execution>
21 <goals>
22 <goal>xjc</goal>
23 </goals>
24 </execution>
25 </executions>
26 <configuration>
27 <!-- The name of your generated source package -->
28 <arguments>-extension -npa -b ${project.basedir}/src/main/xsd/global.xjb</arguments>
29 </configuration>
30 </plugin>
31
32 </plugins>
33 </build>
34
35</project>
在参数中注意global.xjb文件,这就是我们指定 Java 约束规则的地方。
1<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
2<jaxb:bindings version="2.0"
3 xmlns:jaxb="https://java.sun.com/xml/ns/jaxb"
4 xmlns:xjc="https://java.sun.com/xml/ns/jaxb/xjc"
5 xmlns:xs="https://www.w3.org/2001/XMLSchema"
6 jaxb:extensionBindingPrefixes="xjc">
7
8 <jaxb:globalBindings>
9 <xjc:simple />
10 <xjc:serializable uid="-1" />
11 <jaxb:javaType name="java.util.Calendar" xmlType="xs:dateTime"
12 parseMethod="javax.xml.bind.DatatypeConverter.parseDateTime"
13 printMethod="javax.xml.bind.DatatypeConverter.printDateTime" />
14 </jaxb:globalBindings>
15</jaxb:bindings>
以下是将用于生成Java类的XSD。
1<?xml version="1.0" encoding="UTF-8"?>
2<schema xmlns="https://www.w3.org/2001/XMLSchema"
3 targetNamespace="https://www.journaldev.com/com/journaldev/employee/data"
4 xmlns:empns="https://www.journaldev.com/com/journaldev/employee/data"
5 elementFormDefault="qualified">
6
7 <element name="empRequest" type="empns:EmpRequest"></element>
8 <element name="empResponse" type="empns:EmpResponse"></element>
9
10 <complexType name="EmpRequest">
11 <sequence>
12 <element name="id" type="int" minOccurs="0" maxOccurs="1" />
13 <element name="name" type="string" minOccurs="0" maxOccurs="1" />
14 </sequence>
15 </complexType>
16
17 <complexType name="EmpResponse">
18 <sequence>
19 <element name="id" type="int" minOccurs="1" maxOccurs="1" />
20 <element name="name" type="string" minOccurs="1" maxOccurs="1" />
21 <element name="role" type="string" minOccurs="1" maxOccurs="unbounded" />
22 <element name="gender" type="string" minOccurs="1" maxOccurs="1" />
23 <element name="salary" type="string" minOccurs="1" maxOccurs="1" />
24 </sequence>
25 </complexType>
26
27</schema>
Just build the maven project using mvn clean install and you will see java classes generated in target/generated-sources/jaxb directory. Finally the project would look something like below image. 
Further Read: JAXB Tutorial Reference: jaxb2 maven plugin official page, java xjc