SpringMVC 数据绑定实例详解

2019-10-27 17:58:49

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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：