封装fastjson为spring mvc的json view

可以将其中的main方法删掉。测试用的。我测试的结果是，jackson比fastjson快。

fastjson是1.1.36

jackson是2.2.3

jdk是1.7.40，client

cpu是intel i3

内存4g

package org.springframework.web.servlet.view.json;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.StringReader;
import java.io.StringWriter;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.util.CollectionUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.servlet.view.AbstractView;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.parser.Feature;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.test.User;

public class MappingFastJsonView extends AbstractView {
    
    /**
     * Default content type: "application/json".
     * Overridable through {@link #setContentType}.
     */
    public static final String DEFAULT_CONTENT_TYPE = "application/json";

    private String encoding = "UTF-8";
    
    private String jsonPrefix;

    private Boolean prettyPrint;

    private Set<String> modelKeys;

    private boolean extractValueFromSingleKeyModel = false;

    private boolean disableCaching = true;

    private boolean updateContentLength = false;


    /**
     * Construct a new {@code MappingFastJsonView}, setting the content type to {@code application/json}.
     */
    public MappingFastJsonView() {
        setContentType(DEFAULT_CONTENT_TYPE);
        setExposePathVariables(false);
    }
    
    public String getEncoding() {
        return encoding;
    }

    public void setEncoding(String encoding) {
        this.encoding = encoding;
    }

    /**
     * Specify a custom prefix to use for this view's JSON output.
     * Default is none.
     * @see #setPrefixJson
     */
    public void setJsonPrefix(String jsonPrefix) {
        this.jsonPrefix = jsonPrefix;
    }

    /**
     * Indicates whether the JSON output by this view should be prefixed with <tt>"{} && "</tt>.
     * Default is {@code false}.
     * &l