SpringMVC 數據綁定實例詳解

2020-07-27 21:23:45

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SpringMVC 數據綁定

查看spring源碼可以看出spring支持轉換的數據類型：

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);   } }

下面挑選一些常用的數據類型，舉例說明它們的綁定方式

1. 基本數據類型(以int為例，其他類似)：

Controller代碼：

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

JSP表單代碼：

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

表單中input的name值和Controller的參數變量名保持一致，就能完成基本數據類型的數據綁定，如果不一致可以使用@RequestParam標注實現。值得一提的是，如果Controller方法參數中定義的是基本數據類型，但是從jsp提交過來的數據為null或者""的話，會出現數據轉換的異常。也就是說，必須保證表單傳遞過來的數據不能為null或""，所以，在開發過程中，對可能為空的數據，最好將參數數據類型定義成包裝類型，具體參見下面的第二條。

2. 包裝類型(以Integer為例，其他類似)：

Controller代碼：

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

JSP表單代碼：

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

和基本數據類型基本一樣，不同之處在于，JSP表單傳遞過來的數據可以為null或""，以上面代碼為例，如果jsp中num為""或者表單中無num這個input，那么，Controller方法參數中的num值則為null。

3. 自定義對象類型：

Model代碼：

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代碼：

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

JSP表單代碼：

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

非常簡單，只需將對象的屬性名和input的name值一一對應即可。

4. 自定義復合對象類型：

Model代碼：

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代碼：

@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表單代碼：

<form action="test.do" method="post">   <input name="firstName" value="張" /><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對象中有ContactInfo屬性，Controller中的代碼和第3點說的一致，但是，在jsp代碼中，需要使用“屬性名(對象類型的屬性).屬性名”來命名input的name。

5. List綁定：

List需要綁定在對象上，而不能直接寫在Controller方法的參數中。

Model代碼：

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代碼：

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

JSP表單代碼：

<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>

其實，這和第4點User對象中的contantInfo數據的綁定有點類似，但是這里的UserListForm對象里面的屬性被定義成List，而不是普通自定義對象。所以，在JSP中需要指定List的下標。值得一提的是，Spring會創建一個以最大下標值為size的List對象，所以，如果JSP表單中有動態添加行、刪除行的情況，就需要特別注意，譬如一個表格，用戶在使用過程中經過多次刪除行、增加行的操作之后，下標值就會與實際大小不一致，這時候，List中的對象，只有在jsp表單中對應有下標的那些才會有值，否則會為null，看個例子：

JSP表單代碼：

<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>

這個時候，Controller中的userForm.getUsers()獲取到List的size為21，而且這21個User對象都不會為null，但是，第2到第19的User對象中的firstName和lastName都為null。打印結果：

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綁定：

Set和List類似，也需要綁定在對象上，而不能直接寫在Controller方法的參數中。但是，綁定Set數據時，必須先在Set對象中add相應的數量的模型對象。

Model代碼：

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代碼：

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

JSP表單代碼：

<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綁定類似。

需要特別提醒的是，如果最大下標值大于Set的size，則會拋出org.springframework.beans.InvalidPropertyException異常。所以，在使用時有些不便。暫時沒找到解決方法，如果有網友知道，請回帖共享你的做法。

5. Map綁定：

Map最為靈活，它也需要綁定在對象上，而不能直接寫在Controller方法的參數中。

Model代碼：

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代碼：

@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表單代碼：

<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>

打印結果：