SpringMVC 数据绑定实例详解


             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：





@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 



感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！