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发表于 2012-03-19 17:09 |只看该作者 |倒序浏览

digester使用

一.序
  Digester是apache的一个组件 apache commons-digester.jar,通过它可以很方便的从xml文件生成java对象.你不用再象以前通过jdom或者Xerces去读取一个document对象.(jdom和Xerces仍然有它们的用武之地及强大之处,在其它应用里你也少不了它们)
我只是用一个例子展示一下如何把xml文件生成一个java object.
首先你必须把jar加入到你的项目classpath.
(一)准备:
1.环境: Eclipse, jdk1.4+
2.需求说明：学院包含学生和老师，学生可以选修课程，老师有不同的资格认证。
3.Java Class的定义，简洁起见，略去import内容。
4.使用Digester生成java对象必须要定义一个xml文件，此xml文件必须符合digester-rules.dtd的规则。
5.所有的xml文件必须在classpath路径中，这样可以通过Class.getClassLoader().getInputStream()读取xml文件。

(二)提要:
  本示例所需的java class 和 xml文件分成四类:
1.基础xml文件: [academy.xml]: 你将要解析的xml文件.
2.基础java class: [Academy.java, Teacher.java, Student.java, Cousre.java]: 生成的对象的类定义
3.digesterRules.xml: [academyRules.xml]: 定义了基础xml文件到基础java class的匹配(映射)关系
4.Digester class: [DigestXMLJavaAcademy.java]: 根据digesterRules.xml去解析基础xml文件,并生成java 对象

(三)参考资料
1.English ebook: Pro Jakarta Commons by Harshad Oak  Apress 2004

二.基础Java Class
1.学院 class Academy.java

Java代码

1.public class Academy {
2. private Vector students;
3. private Vector teachers;
4. private String name;
5.
6. public Academy() {
7. students = new Vector();
8. teachers = new Vector();
9. }
10.
11. public void addStudent(Student student) {
12. students.addElement(student);
13. }
14.
15. public void addTeacher(Teacher teacher) {
16. teachers.addElement(teacher);
17. }
18.
19. public Vector getStudents() {
20. return students;
21. }
22.
23. public void setStudents(Vector newStudents) {
24. students = newStudents;
25. }
26. public Vector getTeachers() {
27. return teachers;
28. }
29.
30. public void setTeachers(Vector newTeachers) {
31. teachers = newTeachers;
32. }
33.
34. public String getName() {
35. return name;
36. }
37.
38. public void setName(String newName) {
39. name = newName;
40. }
41.}
public class Academy {
private Vector students;
private Vector teachers;
private String name;
public Academy() {
students = new Vector();
teachers = new Vector();
}
public void addStudent(Student student) {
students.addElement(student);
}
public void addTeacher(Teacher teacher) {
teachers.addElement(teacher);
}
public Vector getStudents() {
return students;
}
public void setStudents(Vector newStudents) {
students = newStudents;
}
public Vector getTeachers() {
return teachers;
}
public void setTeachers(Vector newTeachers) {
teachers = newTeachers;
}
public String getName() {
return name;
}
public void setName(String newName) {
name = newName;
}
}

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2.学生 Student.java

Java代码

1.public class Student {
2. private Vector courses;
3. private String name;
4. private String division;
5.
6. public Student() {
7. courses = new Vector();
8. }
9.
10. public void addCourse(Course course) {
11. courses.addElement(course);
12. }
13.
14. public String getName() {
15. return name;
16. }
17. public void setName(String newName) {
18. name = newName;
19. }
20.
21. public String getDivision() {
22. return division;
23. }
24.
25. public void setDivision(String newDivision) {
26. division = newDivision;
27. }
28.
29. public void setCourses(Vector courses) {
30. this.courses = courses;
31. }
32.
33. public Vector getCourses() {
34. return courses;
35. }
36.}
public class Student {
private Vector courses;
private String name;
private String division;
public Student() {
courses = new Vector();
}
public void addCourse(Course course) {
courses.addElement(course);
}
public String getName() {
return name;
}
public void setName(String newName) {
name = newName;
}
public String getDivision() {
return division;
}
public void setDivision(String newDivision) {
division = newDivision;
}
public void setCourses(Vector courses) {
this.courses = courses;
}
public Vector getCourses() {
return courses;
}
}

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3.老师 Teacher.java

Java代码

1.public class Teacher {
2. private String name;
3. private Vector certifications;
4.
5. public Teacher() {
6. certifications = new Vector();
7. }
8.
9. public void addCertification(String certification) {
10. certifications.addElement(certification);
11. }
12.
13. public String getName() {
14. return name;
15. }
16.
17. public void setName(String newName) {
18. name = newName;
19. }
20.
21. public void setCertifications(Vector certifications) {
22. this.certifications = certifications;
23. }
24.
25. public Vector getCertifications() {
26. return certifications;
27. }
28.}
public class Teacher {
private String name;
private Vector certifications;
public Teacher() {
certifications = new Vector();
}
public void addCertification(String certification) {
certifications.addElement(certification);
}
public String getName() {
return name;
}
public void setName(String newName) {
name = newName;
}
public void setCertifications(Vector certifications) {
this.certifications = certifications;
}
public Vector getCertifications() {
return certifications;
}
}

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4.课程 Course.java

Java代码

1.public class Course {
2. private String id;
3. private String name;
4.
5. public Course() {
6. }
7.
8. public String getId() {
9. return id;
10. }
11.
12. public void setId(String newId) {
13. id = newId;
14. }
15. public String getName() {
16. return name;
17. }
18.
19. public void setName(String newName) {
20. name = newName;
21. }
22.}
public class Course {
private String id;
private String name;
public Course() {
}
public String getId() {
return id;
}
public void setId(String newId) {
id = newId;
}
public String getName() {
return name;
}
public void setName(String newName) {
name = newName;
}
}

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三.基础XML文件
============================================================
学院 academy.xml,包含了学生(包含了课程),老师

Java代码

1.<?xml version="1.0"?>
2.<academy name="JAcademy" >
3. <student name="JavaBoy" division="A">
4. <course>
5. <id>C1</id>
6. <name>JSP</name>
7. </course>
8. <course>
9. <id>C2</id>
10. <name>Servlets</name>
11. </course>
12. </student>
13. <student name="JavaGirl" division="B">
14. <course>
15. <id>C3</id>
16. <name>EJB</name>
17. </course>
18. </student>
19.
20. <teacher name="JavaGuru">
21. <certification>SCJP</certification>
22. <certification>SCWCD</certification>
23. </teacher>
24. <teacher name="JavaMaster">
25. <certification>OCP</certification>
26. <certification>SCJP</certification>
27. <certification>SCEA</certification>
28. </teacher>
29.</academy>
<?xml version="1.0"?>
<academy name="JAcademy" >
<student name="JavaBoy" division="A">
<course>
<id>C1</id>
<name>JSP</name>
</course>
<course>
<id>C2</id>
<name>Servlets</name>
</course>
</student>
<student name="JavaGirl" division="B">
<course>
<id>C3</id>
<name>EJB</name>
</course>
</student>
<teacher name="JavaGuru">
<certification>SCJP</certification>
<certification>SCWCD</certification>
</teacher>
<teacher name="JavaMaster">
<certification>OCP</certification>
<certification>SCJP</certification>
<certification>SCEA</certification>
</teacher>
</academy>

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四.Digester Class
DigestXMLJavaAcademy.java 和academyRules.xml
其中academyRules.xml用来定义xml文件和java对象的匹配(映射)关系,格式要符合digester-rules.dtd格式约束
DigestXMLJavaAcademy.java 根据academyRules.xml解析academy.xml文件并生成 Academy对象.

Java代码