springmvc(基础三) Springmvc 数据绑定

来源:http://www.iteye.com/topic/973918

一、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);      }  }  

二、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