那些遇到过的问题

从Controller向JSP页面发送响应时发生异常

Dev*_*eve 1 ajax json jsp controller spring-mvc

我试图从spring mvc控制器发送响应到jsp页面,我得到了一个例外

首先,我尝试将列表返回给jsp页面

列表代码:

@RequestMapping(value = "/Users", method = RequestMethod.POST)
@ResponseBody 
public List<Users> getUsers(@RequestParam(value = "intermediate" ,required = false) String intermediate)throws java.text.ParseException{
    List<Users> list = null;

    int intermediateSelection = Integer.parseInt(intermediate);

    list = getUsersBySelection(IntermediateSelection) //This will return list of users  

    return list;
    }
Run Code Online (Sandbox Code Playgroud)

然后我尝试将JSONObject返回到JSP页面

JSONObject的代码:

@RequestMapping(value = "/Users", method = RequestMethod.POST)
@ResponseBody 
public JSONObject getUsers(@RequestParam(value = "intermediate" ,required = false) String intermediate) throws java.text.ParseException{
    List<Users> list = null;

    int IntermediateSelection = Integer.parseInt(intermediate);

    list = getUsersBySelection(IntermediateSelection);  //This will return list of users

    Iterator<Users> iterator=list.iterator();

    JSONObject UsersJSON = new JSONObject();
    JSONArray usersArray = new JSONArray();

    while (iterator.hasNext()) {
      Users users = iterator.next();

      JSONObject object = new JSONObject();
      object.put("Id", users.getUserId());
      object.put("Name", users.getUserName());
      object.put("Group", users.getGroup());

      usersArray.add(object);
    }

    UsersJSON.put("users", usersArray);

    //System.out.println(UsersJSON.toString());

    return UsersJSON;
    }
Run Code Online (Sandbox Code Playgroud)

他们中的任何一个都不适合我.我有这样的例外.

org.apache.catalina.core.StandardWrapperValve invoke
java.lang.StackOverflowError
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2918)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1174)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1669)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:682)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:132)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:94)
at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:575)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666)
Run Code Online (Sandbox Code Playgroud)

用户Pojo:

@Entity
@Table(name = "Users")
public class Users implements java.io.Serializable {

    private int userId;
    private Role role;
    private Groups groupId;
    private UserType userType;
    private String userName;
    private String password;
    private Boolean isActive;

    public Users() {
    }

    public Users(int userId, Role role, Groups groupId ,UserType userType, String userName, String password, boolean isActive) {
        this.userId = userId;
        this.role = role;
        this.groupId = groupId;
        this.userType = userType;
        this.userName = userName;
        this.password = password;
        this.isActive = isActive;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "UserID", unique = true, nullable = false)
    public int getUserId() {
        return this.userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "RoleID", nullable = false)
    public Role getRole() {
        return this.role;
    }

    public void setRole(Role role) {
        this.role = role;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "GroupId", nullable = false)
    public Groups getGroup() {
        return this.groupId;
    }

    public void setGroup(Groups group) {
        this.groupId = group;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "UserTypeID", nullable = false)
    public UserType getUserType() {
        return this.userType;
    }

    public void setUserType(UserType userType) {
        this.userType = userType;
    }

    @Column(name = "UserName", nullable = false)
    public String getUserName() {
        return this.userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    @Column(name = "Password", nullable = false)
    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Column(name = "IsActive", nullable = false, columnDefinition = "BIT")
    public Boolean isIsActive() {
        return this.isActive;
    }

    public void setIsActive(Boolean isActive) {
        this.isActive = isActive;
    }
}
Run Code Online (Sandbox Code Playgroud)

Luc*_*cky 5

从这篇博文中,

为了让Jackson工作得很好,关系的两个方面之一不应该被序列化,以避免导致StackOverflow错误的恼人的无限递归循环.

因此,Jackson采用引用的前向部分,例如java类的属性(即List<Role>User类中的角色),并将其转换为类似json的存储格式; 这就是所谓的编组过程.然后,杰克逊寻找引用的后面部分(即类中的List<User>用户Role)并保持原样,而不是序列化它.这部分关系将在前向引用的反序列化(解组)期间重新构建.

解:

  1. 添加@JsonManagedReference关系的前向部分(即Users.java类):

  2. 添加@JsonBackReference在关系的后面部分(即Role.java和Groups.java类):

Users.java(示例代码):

@Entity
public class Users implements java.io.Serializable{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "UserID", unique = true, nullable = false)

@Column(name="name")
private String name;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "RoleID", nullable = false)
@JsonManagedReference
public Role getRole() {
    return this.role;
}

...
Run Code Online (Sandbox Code Playgroud)

Role.java(example code):

@Entity
public class Role implements java.io.Serializable {

 @Id 
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 private int id;

 @OneToMany
 @JsonBackReference
 private Set<User> users = new HashSet<User>();

...
Run Code Online (Sandbox Code Playgroud)

同样的方式

Groups.java

@Entity
public class Groups implements java.io.Serializable {

@Id 
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

@ManyToMany(mappedBy="groups")
@JsonBackReference
private Set<User> users = new HashSet<User>();

...
Run Code Online (Sandbox Code Playgroud)

你可以检查的另一个有用的注释是@JsonIdentityInfo:使用它,每次Jackson序列化你的对象时,它会为它添加一个ID(或你选择的另一个属性),这样它就不会每次都完全"扫描"它.当您在更多相互关联的对象(例如:Order -> OrderLine -> User -> Order和重复)之间进行链循环时,这可能很有用.

在这种情况下,您必须要小心,因为您可能需要多次读取对象的属性(例如,在产品列表中包含更多共享同一卖家的产品),并且此注释会阻止您这样做.我建议总是看看firebug日志来检查JSON响应,看看你的代码中发生了什么.

希望这可以帮助.

归档时间：

查看次数：

2109 次

最近记录：

10 年，1 月 前
相关归档
如何手动将Spring MVC视图呈现为html？ 26
如何使用Python将MongoDB的bsondump转换为JSON？ 22
在Groovy中解析JSON数组的数组 17
动态滚动文本区域 14
如何有效地解析C++中的bigdata json文件(wikidata)？ 8
编程Spring MVC控制器和用于HttpDelete的jsp 6
AJAX使用jQuery - 语法错误？ 6
通过AJAX加载内容和预加载图像？ 4
当用户尝试使用浏览器的导航按钮进行导航时,如何强制用户退出？ 4
AJAX Post to ASP.NET MVC 6 Controller操作方法和参数为null 4
难疑归档
从数组创建ArrayList 3441
如何确定变量是"未定义"还是"空"？ 2000
如何在没有换行或空格的情况下打印？ 1760
在jQuery中创建div元素 1500
<meta charset ="utf-8"> vs <meta http-equiv ="Content-Type"> 1499
如何从JavaScript对象中删除密钥？ 1171
HTML中"role"属性的目的是什么？ 1122
如何撤消git reset --hard HEAD~1？ 1083
AngularJS中指令范围内的'@'和'='有什么区别？ 1053
如何在JavaScript中将浮点数转换为整数？ 1043