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 HashMapClass, 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 ListUser> users;
public ListUser> getUsers() {
return users;
}
public void setUsers(ListUser> 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 SetUser> users = new HashSetUser>();
public UserSetForm(){
users.add(new User());
users.add(new User());
users.add(new User());
}
public SetUser> getUsers() {
return users;
}
public void setUsers(SetUser> 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 MapString, User> users;
public MapString, User> getUsers() {
return users;
}
public void setUsers(MapString, User> users) {
this.users = users;
}
}
Controller代碼：
@RequestMapping("test.do")
public void test(UserMapForm userForm) {
for (Map.EntryString, 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：
x: aaa - bbb
y: ccc - ddd
z: eee - fff
感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！
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