Java Map to Json toJSONString(Map map, int indentLevel)

Description

Convert a map to JSON text.

License

Open Source License

Parameter

Parameter	Description
map	a parameter

Return

JSON text, or "null" if map is null.

Declaration

public static <T, U> String toJSONString(Map<T, U> map, int indentLevel) 

Method Source Code

//package com.java2s;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Main {
    /**/*from  w w w  . ja v a 2  s.c o m*/
     * Convert a map to JSON text. The result is a JSON object.
     * 
     * @param map
     * @return JSON text, or "null" if map is null.
     */
    public static <T, U> String toJSONString(Map<T, U> map, int indentLevel) {
        int subIndentLevel = indentLevel + 1;
        if (map == null)
            return getIndent(indentLevel) + "null";

        StringBuffer sb = new StringBuffer();
        boolean first = true;
        Iterator<T> iter = map.keySet().iterator();

        sb.append('{');
        sb.append("\n");
        while (iter.hasNext()) {
            if (first)
                first = false;
            else {
                sb.append(',');
                sb.append("\n");
            }

            T key = iter.next();
            sb.append(getIndent(subIndentLevel));
            sb.append('\"');
            if (String.valueOf(key) == null)
                sb.append("null");
            else
                sb.append(escape(String.valueOf(key)));
            sb.append('\"').append(':');
            sb.append(toJSONString(map.get(key), subIndentLevel));
        }
        sb.append("\n");
        sb.append(getIndent(indentLevel));
        sb.append('}');
        return sb.toString();
    }

    /**
     * Convert a list to JSON text. The result is a JSON array.
     * 
     * @param list
     * @return JSON text, or "null" if list is null.
     */
    public static <T> String toJSONString(List<T> list, int indentLevel) {
        int subIndentLevel = indentLevel + 1;
        if (list == null)
            return getIndent(indentLevel) + "null";

        boolean first = true;
        StringBuffer sb = new StringBuffer();
        Iterator<T> iter = list.iterator();

        sb.append('[');
        sb.append("\n");
        while (iter.hasNext()) {
            if (first)
                first = false;
            else {
                sb.append(',');
                sb.append("\n");
            }

            T value = iter.next();
            sb.append(getIndent(subIndentLevel));
            if (value == null) {
                sb.append("null");
                continue;
            }
            sb.append(toJSONString(value, indentLevel));

        }
        sb.append("\n");
        sb.append(getIndent(indentLevel));
        sb.append(']');

        return sb.toString();
    }

    /**
     * Convert an object to JSON text.
     * 
     * @param value
     * @return JSON text, or "null" if value is null or it's an NaN or an INF number.
     */
    public static String toJSONString(Object value, int indentLevel) {
        if (value == null)
            return "null";

        if (value instanceof String)
            return "\"" + escape((String) value) + "\"";

        if (value instanceof Double) {
            if (((Double) value).isInfinite() || ((Double) value).isNaN())
                return "null";
            else
                return value.toString();
        }

        if (value instanceof Float) {
            if (((Float) value).isInfinite() || ((Float) value).isNaN())
                return "null";
            else
                return value.toString();
        }

        if (value instanceof Number)
            return value.toString();

        if (value instanceof Boolean)
            return value.toString();

        if (value instanceof Map)
            return toJSONString((Map<?, ?>) value, indentLevel);

        if (value instanceof List)
            return toJSONString((List<?>) value, indentLevel);

        return value.toString();
    }

    /**
     * Creates a the indentation that makes JSON Files easier to read
     * 
     * @param indentLevel
     * @return A string Representing the indent spacing
     */
    public static String getIndent(int indentLevel) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < indentLevel; i++) {
            sb.append("    ");
        }
        return sb.toString();
    }

    /**
     * Gets a writable String Escape quotes, \, /, \r, \n, \b, \f, \t and other control characters (U+0000 through U+001F).
     * 
     * @param s
     *            - Must not be null.
     * @return The escaped, writable string
     */
    private static String escape(String s) {
        if (s == null)
            return null;
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            switch (ch) {
            case '"':
                sb.append("\\\"");
                break;
            case '\\':
                sb.append("\\\\");
                break;
            case '\b':
                sb.append("\\b");
                break;
            case '\f':
                sb.append("\\f");
                break;
            case '\n':
                sb.append("\\n");
                break;
            case '\r':
                sb.append("\\r");
                break;
            case '\t':
                sb.append("\\t");
                break;
            case '/':
                sb.append("\\/");
                break;
            default:
                // Reference: http://www.unicode.org/versions/Unicode5.1.0/
                if ((ch >= '\u0000' && ch <= '\u001F') || (ch >= '\u007F' && ch <= '\u009F')
                        || (ch >= '\u2000' && ch <= '\u20FF')) {
                    String ss = Integer.toHexString(ch);
                    sb.append("\\u");
                    for (int k = 0; k < 4 - ss.length(); k++) {
                        sb.append('0');
                    }
                    sb.append(ss.toUpperCase());
                } else {
                    sb.append(ch);
                }
            }
        }
        return sb.toString();
    }
}

Related

1. mapToJson(Map map)
2. toJson(Map map)
3. toJSON(Map map)
4. toJSON(Map map)
5. toJSON(Map map)