[功能]
1. 把 java bean 轉成 xml
2. 把 xml 轉成 java bean
[相依的 component]
大致上同 Digester 的相依性，再加上自己
(如果你只做 bean to xml，大概是用不到 Digester)
[程序]
1. 產生 BeanWriter/BeanReader
BeanWriter beanWriter = new BeanWriter(outputWriter);
BeanReader beanReader = new BeanReader();
2. Configure BeanWriter/BeanReader
beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
beanWriter.getBindingConfiguration().setMapIDs(false);
beanWriter.enablePrettyPrint();
beanReader.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
beanReader.getBindingConfiguration().setMapIDs(false);
3. 執行 write 動作 / 執行 read 動作
beanWriter.write("room", new CustomBean());
CustomBean cbean = (CustomBean) beanReader.parse(xmlReader);
*. ===================================================.*
read 動作之前要先 register bean class
beanReader.registerBeanClass("cbean", CustomBean.class);
參數 1 是 root element name
*. ===================================================.*
4. xml 建立完成 / java instance 建立完成
======================================================================|||||||
[範例] 俺假設要建立的是房客與客戶的資料，房間有編號與容量，客人有姓名和身份證
字號。房間以 Collection 持有客人的資訊。
import java.util.Collection;
/**
* Room bean contain room and customs information
* @author qrtt1
*
*/
public class Room {
private Collection customs;
private Integer number;
private Integer capacity;
public Room() {
}
/**
* @param number the number of this room
* @param capacity how many custom this room can live
*/
public Room(Integer number, Integer capacity) {
assert (number != 0);
assert (capacity != 0);
this.number = number;
this.capacity = capacity;
}
/**
* @param number the number of this room
* @param capacity how many custom this room can live
* @param customs what are customs having lived in
*/
public Room(Integer number, Integer capacity, Collection customs) {
this(number, capacity);
assert (customs != null);
this.customs = customs;
}
/**
* @return the capacity of this room
*/
public Integer getCapacity() {
return this.capacity;
}
/**
* @param capacity set capacity for this room
*/
public void setCapacity(Integer capacity) {
this.capacity = capacity;
}
/**
* @return the customs which live in the room
*/
public Collection getCustoms() {
return this.customs;
}
/**
* @param customs set customs which live in the room
*/
public void setCustoms(Collection customs) {
this.customs = customs;
}
/**
* @return the room no.
*/
public Integer getNumber() {
return this.number;
}
/**
* @param number set room no.
*/
public void setNumber(Integer number) {
this.number = number;
}
/**
* @param c add new custom c
* @return true if still has space for new custom
*/
public boolean addCustom(Custom c){
if( customs.size() < capacity){
return this.customs.add(c);
}
return false;
}
/**
* @param c remove the custom c from this room
* @return true if the custom in this room
*/
public boolean removeCustom(Custom c){
return customs.remove(c);
}
}
/**
* Custom bean store the information of a custom
* @author qrtt1
*
*/
public class Custom {
private String name;
private String id;
public Custom(){}
/**
* @param name custom's name
* @param id custom's id
*/
public Custom(String name, String id) {
assert (name != null && (!"".equals(name)));
assert (id != null && (!"".equals(id)));
this.name = name;
this.id = id;
}
/**
* @return custom's id
*/
public String getId() {
return this.id;
}
/**
* @param id custom's id
*/
public void setId(String id) {
this.id = id;
}
/**
* @return custom's name
*/
public String getName() {
return this.name;
}
/**
* @param name custom's name
*/
public void setName(String name) {
this.name = name;
}
}
接著，為了方便起見，我們建立一個 TestData 類別
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Collection;
import java.util.Vector;
public class TestData {
/**
* @return return out test data
*/
public static Room getData() {
// room no. 103, capacity 8p
Room m = new Room(103, 8);
Collection<Custom> c = new Vector<Custom>();
c.add(new Custom("qrtt1", "A176537653"));
c.add(new Custom("orz", "A2123426543"));
c.add(new Custom("xd", "X123456271"));
m.setCustoms(c);
return m;
}
public static String getXMLData() {
StringBuffer sbuff = new StringBuffer();
String tmp;
try {
FileReader reader = new FileReader("/home/qrtt1/room.xml");
BufferedReader breader = new BufferedReader(reader);
tmp = breader.readLine();
while (tmp != null) {
sbuff.append(tmp);
tmp = breader.readLine();
}
return sbuff.toString();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "";
}
}
==============================================================||||||
讀寫則直接修改手冊裡的範例
import java.io.StringWriter;
public class WriteExampleApp {
/**
* Create an example bean and then convert it to xml.
*/
public static final void main(String [] args) throws Exception {
// Start by preparing the writer
// We'll write to a string
StringWriter outputWriter = new StringWriter();
// Betwixt just writes out the bean as a fragment
// So if we want well-formed xml, we need to add the prolog
outputWriter.write("<?xml version='1.0' ?>\n");
// Create a BeanWriter which writes to our prepared stream
BeanWriter beanWriter = new BeanWriter(outputWriter);
// Configure betwixt
// For more details see java docs or later in the main documentation
beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
beanWriter.getBindingConfiguration().setMapIDs(false);
beanWriter.enablePrettyPrint();
// If the base element is not passed in, Betwixt will guess
// But let's write example bean as base element 'person'
//beanWriter.write("person", new PersonBean("John Smith", 21));
beanWriter.write("room", TestData.getData());
// Write to System.out
// (We could have used the empty constructor for BeanWriter
// but this way is more instructive)
System.out.println(outputWriter.toString());
// Betwixt writes fragments not documents so does not automatically
close
// writers or streams.
// This example will do no more writing so close the writer now.
outputWriter.close();
}
}
import java.io.StringWriter;
public class WriteExampleApp {
/**
* Create an example bean and then convert it to xml.
*/
public static final void main(String [] args) throws Exception {
// Start by preparing the writer
// We'll write to a string
StringWriter outputWriter = new StringWriter();
// Betwixt just writes out the bean as a fragment
// So if we want well-formed xml, we need to add the prolog
outputWriter.write("<?xml version='1.0' ?>\n");
// Create a BeanWriter which writes to our prepared stream
BeanWriter beanWriter = new BeanWriter(outputWriter);
// Configure betwixt
// For more details see java docs or later in the main documentation
beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
beanWriter.getBindingConfiguration().setMapIDs(false);
beanWriter.enablePrettyPrint();
// If the base element is not passed in, Betwixt will guess
// But let's write example bean as base element 'person'
//beanWriter.write("person", new PersonBean("John Smith", 21));
beanWriter.write("room", TestData.getData());
// Write to System.out
// (We could have used the empty constructor for BeanWriter
// but this way is more instructive)
System.out.println(outputWriter.toString());
// Betwixt writes fragments not documents so does not automatically
close
// writers or streams.
// This example will do no more writing so close the writer now.
outputWriter.close();
}
}
=======================================================================
[心得]
1. 讀與寫的 configure 如果不同的話，會發生讀取的錯誤。
2. 請看倌自行 disable configure
-> true 改成 false, false 改成 true 觀察結果。
比較能 make sense
3. 由於 1, 2 的體驗後，你會感到雖然很方便但仍不算實用，
因為 xml 總不是如你預期的樣子，
所以還需要看如何使用客製化設定檔 .betwixt
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