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 

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