在struts 2中将java bean转换为json数据

Question

I have a java bean class 'MenuItem' which consist of list of children . I want to display iterate and render through this object in jsp and display the menu tree. I tried the json data creation, but it needs ajax call. And in my case, I need to submit the page instead of ajax.

I am using struts 2. Can anyone please suggest how can I render and iterate through my bean object in jsp ?

Thanks in Advance.

Here is my Menu bean object:

public class MenuItem implements Serializable {    
    private static final long serialVersionUID = 8690828081102943225L;

    private Long id;
    private String name;
    private Collection<MenuItem> children;
    private String url;
    private String actionHoverLabel;
    private String actionLabel;
    private Long displayOrder;
    private Boolean isLeaf;
    private Boolean isVisible;
    private Long menuLevel;
    private Long parentId;      

    public String getActionHoverLabel() {
        return actionHoverLabel;
    }

    public void setActionHoverLabel(String actionHoverLabel) {
        this.actionHoverLabel = actionHoverLabel;
    }

    public String getActionLabel() {
        return actionLabel;
    }

    public void setActionLabel(String actionLabel) {
        this.actionLabel = actionLabel;
    }

    public Long getDisplayOrder() {
        return displayOrder;
    }

    public void setDisplayOrder(Long displayOrder) {
        this.displayOrder = displayOrder;
    }

    public Boolean getIsLeaf() {
        return isLeaf;
    }

    public void setIsLeaf(Boolean isLeaf) {
        this.isLeaf = isLeaf;
    }

    public Boolean getIsVisible() {
        return isVisible;
    }

    public void setIsVisible(Boolean isVisible) {
        this.isVisible = isVisible;
    }

    public Long getMenuLevel() {
        return menuLevel;
    }

    public void setMenuLevel(Long menuLevel) {
        this.menuLevel = menuLevel;
    }

    public Long getParentId() {
        return parentId;
    }

    public void setParentId(Long parentId) {
        this.parentId = parentId;
    }


    public MenuItem() {
        children = new ArrayList<MenuItem>();
        isVisible = true;
    }

    public MenuItem(Long id, String name) {

        this.id = id;
        this.name = name;
        children = new ArrayList<MenuItem>();
        isVisible = true;
    }

    public Long getId() {    
        return this.id;    
    }

    public void setId(Long id) {
        this.id = id;    
    }

    public String getName() {    
        return this.name;    
    }

    public void setName(String name) {    
        this.name = name;    
    }

    public Collection<MenuItem> getChildren() {

        return this.children;

    }

    public void setChildren(Collection<MenuItem> children) {    
        this.children = children;    
    }


    public boolean isLeaf() {    
        if (children != null && children.size() > 0) {    
            return false;    
        } else {    
            return true;    
        }    
    }

    public void addChild(MenuItem child) {    
        if (child != null && children != null) {    
            children.add(child);
            child.setParentId(this.getId());    
        }    
    }

    public void removeChild(MenuItem child) {    
        if (child != null && children != null) {    
            children.remove(child);
            child.setParentId(null);    
        }    
    }       

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUrl() {
        if (url == null) {
            return name;
        } else {
            return url;
        }
    }


    @Override
    public boolean equals(Object obj) {
        MenuItem m = null;
        boolean isEqual = false;    
        if (id != null && id >= 0) {
            m = (MenuItem) obj;
            if (m.getId().equals(id) 
                    isEqual = true;                     
        } else {    
            isEqual = super.equals(obj);    
        }    
        return isEqual;    
    }

    @Override
    public int hashCode() {    
        if (id != null && id >= 0) {    
            return id.hashCode();    
        } else {    
            return super.hashCode();    
        }    
    }

    @Override
    public String toString() {    
        return "name: " + name + " id: " + id;    
    }

Answer 1

Go to www.json.org

Download Java Library for JSON encoding.

Compile it (build a jar for convenience).

Write a method alike this to JSON Serialize your bean:

 public static String toJson(SomeBean bean) 
 {
        JSONObject jo = new JSONObject(bean);
        return jo.toString();
 }

Deserialization is a little tricky but should work like:

JSONObject jo = new JSONObject(jsonString);
SomeBean res = new SomeBean();

res.someProperty = jo.getString("someProperty");
res.someIntProperty= jo.getInt("someIntProperty");

Obviously you have to take care of complex properties, but for simple beans it should work out like a charm.

Straight from sources:

/**
     * Construct a JSONObject from an Object using bean getters.
     * It reflects on all of the public methods of the object.
     * For each of the methods with no parameters and a name starting
     * with <code>"get"</code> or <code>"is"</code> followed by an uppercase letter,
     * the method is invoked, and a key and the value returned from the getter method
     * are put into the new JSONObject.
     *
     * The key is formed by removing the <code>"get"</code> or <code>"is"</code> prefix.
     * If the second remaining character is not upper case, then the first
     * character is converted to lower case.
     *
     * For example, if an object has a method named <code>"getName"</code>, and
     * if the result of calling <code>object.getName()</code> is <code>"Larry Fine"</code>,
     * then the JSONObject will contain <code>"name": "Larry Fine"</code>.
     *
     * @param bean An object that has getter methods that should be used
     * to make a JSONObject.
     */
    public JSONObject(Object bean) {
        this();
        this.populateMap(bean);
    }

Are you sure you've everything set up correctly (Classpath) ?

Answer 2

If you want to operate on the bean in JSP, you can very well do that with struts tags. The bean has to be in the scope.

Why do you need JSON in this case? If you still want JSON, the check for GSON library and Jackson mapper library. On the JSP, you can store the JSON object in a variable and then operate on that. On page submit Struts action would form the JSON and then set it in a page bean variable.