浅谈 SpringMVC 数据绑定

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:

[java] view plain copy print ?
  1. @RequestMapping("test.do"
  2. public void test(Integer num) { 
  3.      


    JSP表单代码:

[java] view plain copy print ?
  1. <form action="test.do" method="post"
  2.    <input name="num" value="10" type="text"/> 
  3.    ...... 
  4. </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:

[java] view plain copy print ?
  1. public class User { 
  2.  
  3.     private String firstName; 
  4.  
  5.     private String lastName; 
  6.  
  7.     public String getFirstName() { 
  8.         return firstName; 
  9.     } 
  10.  
  11.     public void setFirstName(String firstName) { 
  12.         this.firstName = firstName; 
  13.     } 
  14.  
  15.     public String getLastName() { 
  16.         return lastName; 
  17.     } 
  18.  
  19.     public void setLastName(String lastName) { 
  20.         this.lastName = lastName; 
  21.     } 
  22.  


    Controller代码:

[java] view plain copy print ?
  1. @RequestMapping("test.do"
  2. public void test(User user) { 
  3.      


    JSP表单代码:

[java] view plain copy print ?
  1. <form action="test.do" method="post"
  2.    <input name="firstName" value="张" type="text"/> 
  3.    <input name="lastName" value="三" type="text"/> 
  4.    ...... 
  5. </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:

 
  1. public class ContactInfo { 
  2.  
  3.     private String tel; 
  4.  
  5.     private String address; 
  6.  
  7.     public String getTel() { 
  8.         return tel; 
  9.     } 
  10.  
  11.     public void setTel(String tel) { 
  12.         this.tel = tel; 
  13.     } 
  14.  
  15.     public String getAddress() { 
  16.         return address; 
  17.     } 
  18.  
  19.     public void setAddress(String address) { 
  20.         this.address = address; 
  21.     } 
  22.  
  23.  
  24. public class User { 
  25.  
  26.     private String firstName; 
  27.  
  28.     private String lastName; 
  29.  
  30.     private ContactInfo contactInfo; 
  31.  
  32.     public String getFirstName() { 
  33.         return firstName; 
  34.     } 
  35.  
  36.     public void setFirstName(String firstName) { 
  37.         this.firstName = firstName; 
  38.     } 
  39.  
  40.     public String getLastName() { 
  41.         return lastName; 
  42.     } 
  43.  
  44.     public void setLastName(String lastName) { 
  45.         this.lastName = lastName; 
  46.     } 
  47.  
  48.     public ContactInfo getContactInfo() { 
  49.         return contactInfo; 
  50.     } 
  51.  
  52.     public void setContactInfo(ContactInfo contactInfo) { 
  53.         this.contactInfo = contactInfo; 
  54.     } 
  55.  


    Controller代码:

 
  1. @RequestMapping("test.do"
  2. public void test(User user) { 
  3.     System.out.println(user.getFirstName()); 
  4.     System.out.println(user.getLastName()); 
  5.     System.out.println(user.getContactInfo().getTel()); 
  6.     System.out.println(user.getContactInfo().getAddress()); 


    JSP表单代码:

[java] view plain copy print ?
  1. <form action="test.do" method="post"
  2.    <input name="firstName" value="张" /><br> 
  3.    <input name="lastName" value="三" /><br> 
  4.    <input name="contactInfo.tel" value="13809908909" /><br> 
  5.    <input name="contactInfo.address" value="北京海淀" /><br> 
  6.    <input type="submit" value="Save" /> 
  7. </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:

 
  1. public class User { 
  2.  
  3.     private String firstName; 
  4.  
  5.     private String lastName; 
  6.  
  7.     public String getFirstName() { 
  8.         return firstName; 
  9.     } 
  10.  
  11.     public void setFirstName(String firstName) { 
  12.         this.firstName = firstName; 
  13.     } 
  14.  
  15.     public String getLastName() { 
  16.         return lastName; 
  17.     } 
  18.  
  19.     public void setLastName(String lastName) { 
  20.         this.lastName = lastName; 
  21.     } 
  22.  
  23.  
  24.        public class UserListForm { 
  25.  
  26.     private List<User> users; 
  27.  
  28.     public List<User> getUsers() { 
  29.         return users; 
  30.     } 
  31.  
  32.     public void setUsers(List<User> users) { 
  33.         this.users = users; 
  34.     } 
  35.  


    Controller代码:

  1. @RequestMapping("test.do"
  2. public void test(UserListForm userForm) { 
  3.     for (User user : userForm.getUsers()) { 
  4.         System.out.println(user.getFirstName() + " - " + user.getLastName()); 
  5.     } 


    JSP表单代码:

  1. <form action="test.do" method="post"
  2.    <table> 
  3.       <thead> 
  4.          <tr> 
  5.             <th>First Name</th> 
  6.             <th>Last Name</th> 
  7.          </tr> 
  8.       </thead> 
  9.       <tfoot> 
  10.          <tr> 
  11.             <td colspan="2"><input type="submit" value="Save" /></td> 
  12.          </tr> 
  13.       </tfoot> 
  14.       <tbody> 
  15.          <tr> 
  16.             <td><input name="users[0].firstName" value="aaa" /></td> 
  17.             <td><input name="users[0].lastName" value="bbb" /></td> 
  18.          </tr> 
  19.          <tr> 
  20.             <td><input name="users[1].firstName" value="ccc" /></td> 
  21.             <td><input name="users[1].lastName" value="ddd" /></td> 
  22.          </tr> 
  23.          <tr> 
  24.             <td><input name="users[2].firstName" value="eee" /></td> 
  25.             <td><input name="users[2].lastName" value="fff" /></td> 
  26.          </tr> 
  27.       </tbody> 
  28.    </table> 
  29. </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:

[java] view plain copy print ?
  1. <form action="test.do" method="post"
  2.    <table> 
  3.       <thead> 
  4.          <tr> 
  5.             <th>First Name</th> 
  6.             <th>Last Name</th> 
  7.          </tr> 
  8.       </thead> 
  9.       <tfoot> 
  10.          <tr> 
  11.             <td colspan="2"><input type="submit" value="Save" /></td> 
  12.          </tr> 
  13.       </tfoot> 
  14.       <tbody> 
  15.          <tr> 
  16.             <td><input name="users[0].firstName" value="aaa" /></td> 
  17.             <td><input name="users[0].lastName" value="bbb" /></td> 
  18.          </tr> 
  19.          <tr> 
  20.             <td><input name="users[1].firstName" value="ccc" /></td> 
  21.             <td><input name="users[1].lastName" value="ddd" /></td> 
  22.          </tr> 
  23.          <tr> 
  24.             <td><input name="users[20].firstName" value="eee" /></td> 
  25.             <td><input name="users[20].lastName" value="fff" /></td> 
  26.          </tr> 
  27.       </tbody> 
  28.    </table> 
  29. </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:

[java] view plain copy print ?
  1. aaa - bbb 
  2. ccc - ddd 
  3. null - null 
  4. null - null 
  5. null - null 
  6. null - null 
  7. null - null 
  8. null - null 
  9. null - null 
  10. null - null 
  11. null - null 
  12. null - null 
  13. null - null 
  14. null - null 
  15. null - null 
  16. null - null 
  17. null - null 
  18. null - null 
  19. null - null 
  20. null - null 
  21. 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:

  1. public class User { 
  2.  
  3.     private String firstName; 
  4.  
  5.     private String lastName; 
  6.  
  7.     public String getFirstName() { 
  8.         return firstName; 
  9.     } 
  10.  
  11.     public void setFirstName(String firstName) { 
  12.         this.firstName = firstName; 
  13.     } 
  14.  
  15.     public String getLastName() { 
  16.         return lastName; 
  17.     } 
  18.  
  19.     public void setLastName(String lastName) { 
  20.         this.lastName = lastName; 
  21.     } 
  22.  
  23.  
  24. public class UserSetForm { 
  25.  
  26.     private Set<User> users = new HashSet<User>(); 
  27.      
  28.     public UserSetForm(){ 
  29.         users.add(new User()); 
  30.         users.add(new User()); 
  31.         users.add(new User()); 
  32.     } 
  33.  
  34.     public Set<User> getUsers() { 
  35.         return users; 
  36.     } 
  37.  
  38.     public void setUsers(Set<User> users) { 
  39.         this.users = users; 
  40.     } 
  41.  


    Controller代码:

  1. @RequestMapping("test.do"
  2. public void test(UserSetForm userForm) { 
  3.     for (User user : userForm.getUsers()) { 
  4.         System.out.println(user.getFirstName() + " - " + user.getLastName()); 
  5.     } 


    JSP表单代码:

[java] view plain copy print ?
  1. <form action="test.do" method="post"
  2.    <table> 
  3.       <thead> 
  4.          <tr> 
  5.             <th>First Name</th> 
  6.             <th>Last Name</th> 
  7.          </tr> 
  8.       </thead> 
  9.       <tfoot> 
  10.          <tr> 
  11.             <td colspan="2"><input type="submit" value="Save" /></td> 
  12.          </tr> 
  13.       </tfoot> 
  14.       <tbody> 
  15.          <tr> 
  16.             <td><input name="users[0].firstName" value="aaa" /></td> 
  17.             <td><input name="users[0].lastName" value="bbb" /></td> 
  18.          </tr> 
  19.          <tr> 
  20.             <td><input name="users[1].firstName" value="ccc" /></td> 
  21.             <td><input name="users[1].lastName" value="ddd" /></td> 
  22.          </tr> 
  23.          <tr> 
  24.             <td><input name="users[2].firstName" value="eee" /></td> 
  25.             <td><input name="users[2].lastName" value="fff" /></td> 
  26.          </tr> 
  27.       </tbody> 
  28.    </table> 
  29. </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:

  1. public class User { 
  2.  
  3.     private String firstName; 
  4.  
  5.     private String lastName; 
  6.  
  7.     public String getFirstName() { 
  8.         return firstName; 
  9.     } 
  10.  
  11.     public void setFirstName(String firstName) { 
  12.         this.firstName = firstName; 
  13.     } 
  14.  
  15.     public String getLastName() { 
  16.         return lastName; 
  17.     } 
  18.  
  19.     public void setLastName(String lastName) { 
  20.         this.lastName = lastName; 
  21.     } 
  22.  
  23.  
  24. public class UserMapForm { 
  25.  
  26.     private Map<String, User> users; 
  27.  
  28.     public Map<String, User> getUsers() { 
  29.         return users; 
  30.     } 
  31.  
  32.     public void setUsers(Map<String, User> users) { 
  33.         this.users = users; 
  34.     } 
  35.  


    Controller代码:

 
  1. @RequestMapping("test.do"
  2. public void test(UserMapForm userForm) { 
  3.     for (Map.Entry<String, User> entry : userForm.getUsers().entrySet()) { 
  4.         System.out.println(entry.getKey() + ": " + entry.getValue().getFirstName() + " - "
  5.                                  entry.getValue().getLastName()); 
  6.     } 


    JSP表单代码:

  1. <form action="test.do" method="post"
  2.    <table> 
  3.       <thead> 
  4.          <tr> 
  5.             <th>First Name</th> 
  6.             <th>Last Name</th> 
  7.          </tr> 
  8.       </thead> 
  9.       <tfoot> 
  10.          <tr> 
  11.             <td colspan="2"><input type="submit" value="Save" /></td> 
  12.          </tr> 
  13.       </tfoot> 
  14.       <tbody> 
  15.          <tr> 
  16.             <td><input name="users['x'].firstName" value="aaa" /></td> 
  17.             <td><input name="users['x'].lastName" value="bbb" /></td> 
  18.          </tr> 
  19.          <tr> 
  20.             <td><input name="users['y'].firstName" value="ccc" /></td> 
  21.             <td><input name="users['y'].lastName" value="ddd" /></td> 
  22.          </tr> 
  23.          <tr> 
  24.             <td><input name="users['z'].firstName" value="eee" /></td> 
  25.             <td><input name="users['z'].lastName" value="fff" /></td> 
  26.          </tr> 
  27.       </tbody> 
  28.    </table> 
  29. </form> 


打印结果:

  1. x: aaa - bbb 
  2. y: ccc - ddd 
  3. z: eee - fff 

 

 

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