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浅谈 SpringMVC 数据绑定

2011-03-28 13:00 435 查看

查看spring源码可以看出spring支持转换的数据类型：
org.springframework.beans.PropertyEditorRegistrySupport:

/**
	 * Actually register the default editors for this registry instance.
	 */
	private void createDefaultEditors() {
		this.defaultEditors = new HashMap<Class, PropertyEditor>(64);

		// Simple editors, without parameterization capabilities.
		// The JDK does not contain a default editor for any of these target types.
		this.defaultEditors.put(Charset.class, new CharsetEditor());
		this.defaultEditors.put(Class.class, new ClassEditor());
		this.defaultEditors.put(Class[].class, new ClassArrayEditor());
		this.defaultEditors.put(Currency.class, new CurrencyEditor());
		this.defaultEditors.put(File.class, new FileEditor());
		this.defaultEditors.put(InputStream.class, new InputStreamEditor());
		this.defaultEditors.put(InputSource.class, new InputSourceEditor());
		this.defaultEditors.put(Locale.class, new LocaleEditor());
		this.defaultEditors.put(Pattern.class, new PatternEditor());
		this.defaultEditors.put(Properties.class, new PropertiesEditor());
		this.defaultEditors.put(Resource[].class, new ResourceArrayPropertyEditor());
		this.defaultEditors.put(TimeZone.class, new TimeZoneEditor());
		this.defaultEditors.put(URI.class, new URIEditor());
		this.defaultEditors.put(URL.class, new URLEditor());
		this.defaultEditors.put(UUID.class, new UUIDEditor());

		// Default instances of collection editors.
		// Can be overridden by registering custom instances of those as custom editors.
		this.defaultEditors.put(Collection.class, new CustomCollectionEditor(Collection.class));
		this.defaultEditors.put(Set.class, new CustomCollectionEditor(Set.class));
		this.defaultEditors.put(SortedSet.class, new CustomCollectionEditor(SortedSet.class));
		this.defaultEditors.put(List.class, new CustomCollectionEditor(List.class));
		this.defaultEditors.put(SortedMap.class, new CustomMapEditor(SortedMap.class));

		// Default editors for primitive arrays.
		this.defaultEditors.put(byte[].class, new ByteArrayPropertyEditor());
		this.defaultEditors.put(char[].class, new CharArrayPropertyEditor());

		// The JDK does not contain a default editor for char!
		this.defaultEditors.put(char.class, new CharacterEditor(false));
		this.defaultEditors.put(Character.class, new CharacterEditor(true));

		// Spring's CustomBooleanEditor accepts more flag values than the JDK's default editor.
		this.defaultEditors.put(boolean.class, new CustomBooleanEditor(false));
		this.defaultEditors.put(Boolean.class, new CustomBooleanEditor(true));

		// The JDK does not contain default editors for number wrapper types!
		// Override JDK primitive number editors with our own CustomNumberEditor.
		this.defaultEditors.put(byte.class, new CustomNumberEditor(Byte.class, false));
		this.defaultEditors.put(Byte.class, new CustomNumberEditor(Byte.class, true));
		this.defaultEditors.put(short.class, new CustomNumberEditor(Short.class, false));
		this.defaultEditors.put(Short.class, new CustomNumberEditor(Short.class, true));
		this.defaultEditors.put(int.class, new CustomNumberEditor(Integer.class, false));
		this.defaultEditors.put(Integer.class, new CustomNumberEditor(Integer.class, true));
		this.defaultEditors.put(long.class, new CustomNumberEditor(Long.class, false));
		this.defaultEditors.put(Long.class, new CustomNumberEditor(Long.class, true));
		this.defaultEditors.put(float.class, new CustomNumberEditor(Float.class, false));
		this.defaultEditors.put(Float.class, new CustomNumberEditor(Float.class, true));
		this.defaultEditors.put(double.class, new CustomNumberEditor(Double.class, false));
		this.defaultEditors.put(Double.class, new CustomNumberEditor(Double.class, true));
		this.defaultEditors.put(BigDecimal.class, new CustomNumberEditor(BigDecimal.class, true));
		this.defaultEditors.put(BigInteger.class, new CustomNumberEditor(BigInteger.class, true));

		// Only register config value editors if explicitly requested.
		if (this.configValueEditorsActive) {
			StringArrayPropertyEditor sae = new StringArrayPropertyEditor();
			this.defaultEditors.put(String[].class, sae);
			this.defaultEditors.put(short[].class, sae);
			this.defaultEditors.put(int[].class, sae);
			this.defaultEditors.put(long[].class, sae);
		}
	}

下面挑选一些常用的数据类型，举例说明它们的绑定方式

1. 基本数据类型(以int为例，其他类似)：
Controller代码：

@RequestMapping("test.do")
	public void test(int num) {
		
	}

JSP表单代码：

<form action="test.do" method="post">
         <input name="num" value="10" type="text"/>
         ......
      </form>

表单中input的name值和Controller的参数变量名保持一致，就能完成基本数据类型的数据绑定，如果不一致可以使用@RequestParam标注实现。值得一提的是，如果Controller方法参数中定义的是基本数据类型，但是从jsp提交过来的数据为null或者""的话，会出现数据转换的异常。也就是说，必须保证表单传递过来的数据不能为null或""，所以，在开发过程中，对可能为空的数据，最好将参数数据类型定义成包装类型，具体参见下面的第二条。

2. 包装类型(以Integer为例，其他类似)：
Controller代码：

@RequestMapping("test.do")
	public void test(Integer num) {
		
	}

JSP表单代码：

<form action="test.do" method="post">
         <input name="num" value="10" type="text"/>
         ......
      </form>

和基本数据类型基本一样，不同之处在于，JSP表单传递过来的数据可以为null或""，以上面代码为例，如果jsp中num为""或者表单中无num这个input，那么，Controller方法参数中的num值则为null。

3. 自定义对象类型：
Model代码：

public class User {
	
		private String firstName;
	
		private String lastName;
	
		public String getFirstName() {
			return firstName;
		}
	
		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}
	
		public String getLastName() {
			return lastName;
		}
	
		public void setLastName(String lastName) {
			this.lastName = lastName;
		}
	
	}

Controller代码：

@RequestMapping("test.do")
	public void test(User user) {
		
	}

JSP表单代码：

<form action="test.do" method="post">
         <input name="firstName" value="张" type="text"/>
         <input name="lastName" value="三" type="text"/>
         ......
      </form>

非常简单，只需将对象的属性名和input的name值一一对应即可。

4. 自定义复合对象类型：
Model代码：

public class ContactInfo {
	
		private String tel;
	
		private String address;
	
		public String getTel() {
			return tel;
		}
	
		public void setTel(String tel) {
			this.tel = tel;
		}
	
		public String getAddress() {
			return address;
		}
	
		public void setAddress(String address) {
			this.address = address;
		}
	
	}

	public class User {
	
		private String firstName;
	
		private String lastName;
	
		private ContactInfo contactInfo;
	
		public String getFirstName() {
			return firstName;
		}
	
		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}
	
		public String getLastName() {
			return lastName;
		}
	
		public void setLastName(String lastName) {
			this.lastName = lastName;
		}
	
		public ContactInfo getContactInfo() {
			return contactInfo;
		}
	
		public void setContactInfo(ContactInfo contactInfo) {
			this.contactInfo = contactInfo;
		}
	
	}

Controller代码：

@RequestMapping("test.do")
	public void test(User user) {
		System.out.println(user.getFirstName());
		System.out.println(user.getLastName());
		System.out.println(user.getContactInfo().getTel());
		System.out.println(user.getContactInfo().getAddress());
	}

JSP表单代码：

<form action="test.do" method="post">
         <input name="firstName" value="张" /><br>
         <input name="lastName" value="三" /><br>
         <input name="contactInfo.tel" value="13809908909" /><br>
         <input name="contactInfo.address" value="北京海淀" /><br>
         <input type="submit" value="Save" />
      </form>

User对象中有ContactInfo属性，Controller中的代码和第3点说的一致，但是，在jsp代码中，需要使用“属性名(对象类型的属性).属性名”来命名input的name。

5. List绑定：
List需要绑定在对象上，而不能直接写在Controller方法的参数中。
Model代码：

public class User {
	
		private String firstName;
	
		private String lastName;
	
		public String getFirstName() {
			return firstName;
		}
	
		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}
	
		public String getLastName() {
			return lastName;
		}
	
		public void setLastName(String lastName) {
			this.lastName = lastName;
		}
	
	}
        public class UserListForm {
	
		private List<User> users;
	
		public List<User> getUsers() {
			return users;
		}
	
		public void setUsers(List<User> users) {
			this.users = users;
		}
	
	}

Controller代码：

@RequestMapping("test.do")
	public void test(UserListForm userForm) {
		for (User user : userForm.getUsers()) {
			System.out.println(user.getFirstName() + " - " + user.getLastName());
		}
	}

JSP表单代码：

<form action="test.do" method="post">
         <table>
            <thead>
               <tr>
                  <th>First Name</th>
                  <th>Last Name</th>
               </tr>
            </thead>
            <tfoot>
               <tr>
                  <td colspan="2"><input type="submit" value="Save" /></td>
               </tr>
            </tfoot>
            <tbody>
               <tr>
                  <td><input name="users[0].firstName" value="aaa" /></td>
                  <td><input name="users[0].lastName" value="bbb" /></td>
               </tr>
               <tr>
                  <td><input name="users[1].firstName" value="ccc" /></td>
                  <td><input name="users[1].lastName" value="ddd" /></td>
               </tr>
               <tr>
                  <td><input name="users[2].firstName" value="eee" /></td>
                  <td><input name="users[2].lastName" value="fff" /></td>
               </tr>
            </tbody>
         </table>
      </form>

其实，这和第4点User对象中的contantInfo数据的绑定有点类似，但是这里的UserListForm对象里面的属性被定义成List，而不是普通自定义对象。所以，在JSP中需要指定List的下标。值得一提的是，Spring会创建一个以最大下标值为size的List对象，所以，如果JSP表单中有动态添加行、删除行的情况，就需要特别注意，譬如一个表格，用户在使用过程中经过多次删除行、增加行的操作之后，下标值就会与实际大小不一致，这时候，List中的对象，只有在jsp表单中对应有下标的那些才会有值，否则会为null，看个例子：
JSP表单代码：

<form action="test.do" method="post">
         <table>
            <thead>
               <tr>
                  <th>First Name</th>
                  <th>Last Name</th>
               </tr>
            </thead>
            <tfoot>
               <tr>
                  <td colspan="2"><input type="submit" value="Save" /></td>
               </tr>
            </tfoot>
            <tbody>
               <tr>
                  <td><input name="users[0].firstName" value="aaa" /></td>
                  <td><input name="users[0].lastName" value="bbb" /></td>
               </tr>
               <tr>
                  <td><input name="users[1].firstName" value="ccc" /></td>
                  <td><input name="users[1].lastName" value="ddd" /></td>
               </tr>
               <tr>
                  <td><input name="users[20].firstName" value="eee" /></td>
                  <td><input name="users[20].lastName" value="fff" /></td>
               </tr>
            </tbody>
         </table>
      </form>

这个时候，Controller中的userForm.getUsers()获取到List的size为21，而且这21个User对象都不会为null，但是，第2到第19的User对象中的firstName和lastName都为null。打印结果：

aaa - bbb
ccc - ddd
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
null - null
eee - fff

6. Set绑定：
Set和List类似，也需要绑定在对象上，而不能直接写在Controller方法的参数中。但是，绑定Set数据时，必须先在Set对象中add相应的数量的模型对象。
Model代码：

public class User {
	
		private String firstName;
	
		private String lastName;
	
		public String getFirstName() {
			return firstName;
		}
	
		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}
	
		public String getLastName() {
			return lastName;
		}
	
		public void setLastName(String lastName) {
			this.lastName = lastName;
		}
	
	}
	public class UserSetForm {
	
		private Set<User> users = new HashSet<User>();
		
		public UserSetForm(){
			users.add(new User());
			users.add(new User());
			users.add(new User());
		}
	
		public Set<User> getUsers() {
			return users;
		}
	
		public void setUsers(Set<User> users) {
			this.users = users;
		}
	
	}

Controller代码：

@RequestMapping("test.do")
	public void test(UserSetForm userForm) {
		for (User user : userForm.getUsers()) {
			System.out.println(user.getFirstName() + " - " + user.getLastName());
		}
	}

JSP表单代码：

<form action="test.do" method="post">
         <table>
            <thead>
               <tr>
                  <th>First Name</th>
                  <th>Last Name</th>
               </tr>
            </thead>
            <tfoot>
               <tr>
                  <td colspan="2"><input type="submit" value="Save" /></td>
               </tr>
            </tfoot>
            <tbody>
               <tr>
                  <td><input name="users[0].firstName" value="aaa" /></td>
                  <td><input name="users[0].lastName" value="bbb" /></td>
               </tr>
               <tr>
                  <td><input name="users[1].firstName" value="ccc" /></td>
                  <td><input name="users[1].lastName" value="ddd" /></td>
               </tr>
               <tr>
                  <td><input name="users[2].firstName" value="eee" /></td>
                  <td><input name="users[2].lastName" value="fff" /></td>
               </tr>
            </tbody>
         </table>
      </form>

基本和List绑定类似。
需要特别提醒的是，如果最大下标值大于Set的size，则会抛出org.springframework.beans.InvalidPropertyException异常。所以，在使用时有些不便。暂时没找到解决方法，如果有网友知道，请回帖共享你的做法。

5. Map绑定：
Map最为灵活，它也需要绑定在对象上，而不能直接写在Controller方法的参数中。
Model代码：

public class User {
	
		private String firstName;
	
		private String lastName;
	
		public String getFirstName() {
			return firstName;
		}
	
		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}
	
		public String getLastName() {
			return lastName;
		}
	
		public void setLastName(String lastName) {
			this.lastName = lastName;
		}
	
	}
	public class UserMapForm {
	
		private Map<String, User> users;
	
		public Map<String, User> getUsers() {
			return users;
		}
	
		public void setUsers(Map<String, User> users) {
			this.users = users;
		}
	
	}

Controller代码：

@RequestMapping("test.do")
	public void test(UserMapForm userForm) {
		for (Map.Entry<String, User> entry : userForm.getUsers().entrySet()) {
			System.out.println(entry.getKey() + ": " + entry.getValue().getFirstName() + " - " +
                                  entry.getValue().getLastName());
		}
	}

JSP表单代码：

<form action="test.do" method="post">
         <table>
            <thead>
               <tr>
                  <th>First Name</th>
                  <th>Last Name</th>
               </tr>
            </thead>
            <tfoot>
               <tr>
                  <td colspan="2"><input type="submit" value="Save" /></td>
               </tr>
            </tfoot>
            <tbody>
               <tr>
                  <td><input name="users['x'].firstName" value="aaa" /></td>
                  <td><input name="users['x'].lastName" value="bbb" /></td>
               </tr>
               <tr>
                  <td><input name="users['y'].firstName" value="ccc" /></td>
                  <td><input name="users['y'].lastName" value="ddd" /></td>
               </tr>
               <tr>
                  <td><input name="users['z'].firstName" value="eee" /></td>
                  <td><input name="users['z'].lastName" value="fff" /></td>
               </tr>
            </tbody>
         </table>
      </form>

打印结果：

x: aaa - bbb
y: ccc - ddd
z: eee - fff

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