jackson 完整Jar包

Jackson fasterxml和codehaus的区别： 他们是Jackson的两大分支、也是两个版本的不同包名。Jackson从2.0开始改用新的包名fasterxml；

1.x版本的包名是codehaus。除了包名不同，他们的Maven artifact id也不同。1.x版本现在只提供bug-fix，

2.x版本还在不断开发和发布中。如果是新项目，建议直接用2x，即fasterxml jackson。

P.S. Jackson可以轻松的将Java对象转换成json对象和xml文档，同样也可以将json、xml转换成Java对象。

官网：http://wiki.fasterxml.com/JacksonHome 三个主要的模块： jackson-co re：核心包 jackson-annotations：注解包 jackson-databind：数据绑定包 jackson-databind需要引用另外两个包，所以如果项目中需要jackson-databind，则只需要加入它的dependency就行了，其他两个会自动引入： <dependency> <groupId>com.fasterxml.jackson.

使用(java jar-jackson-all-1.9.0jar自行下载)

import java.io.StringWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;  

import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.DeserializationConfig.Feature;
import org.codehaus.jackson.map.MappingJsonFactory;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.JavaType;  

public class JsonUtils {  

    public static <K, V> String toJson(Map<K, V> obj) {
        String jsonString = "";
        try {
            if (obj == null) {
                return "";
            }
            StringWriter sw = new StringWriter();
            JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
            ObjectMapper mapper = new ObjectMapper();
            mapper.writeValue(gen, obj);
            jsonString = sw.toString();
            sw.close();
        } catch (Exception ex) {
            ex.printStackTrace();
            return "";
        }  

        return jsonString;
    }  

    @SuppressWarnings("unchecked")
    public static Map<String, Object> toMap(String json) {
        Map<String, Object> result = new HashMap<String, Object>();
        try {
            if (json == null || json.equals("")) {
                return null;
            }  

            ObjectMapper objectMapper = new ObjectMapper();
            result = objectMapper.readValue(json, Map.class);
            if (result == null) {
                return new HashMap<String, Object>();
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }  

        return result;
    }  

    public static String toJson(Object object) {
        String json = "";
        try {
            if (object == null) {
                return "";
            }
            StringWriter sw = new StringWriter();
            JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
            ObjectMapper mapper = new ObjectMapper();  

            mapper.writeValue(gen, object);  

            json = sw.toString();
            sw.close();
        } catch (Exception ex) {
            ex.printStackTrace();
            json = "";
        }
        return json;
    }  

    public static <T> T toObject(String json, Class<T> clazz) {
        T obj = null;
        try {
            if (json == null || json.equals("")) {
                return null;
            }
            JsonFactory jsonFactory = new MappingJsonFactory();
            JsonParser jsonParser = jsonFactory.createJsonParser(json);
            ObjectMapper mapper = new ObjectMapper();
    mapper.configure(Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
            //mapper.getDeserializationConfig().set(Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
            obj = mapper.readValue(jsonParser, clazz);  

        } catch (Exception ex) {
            ex.printStackTrace();
            obj = null;
        }
        return obj;  

    }  

    public static <T> List<T> toList(String json, Class<T> clazz) {
        if (json == null || json.equals("")) {
            return null;
        }
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
        List<T> list = new ArrayList<T>();
        try {
            JavaType type = mapper.getTypeFactory().constructParametricType(List.class, clazz);
            list = mapper.readValue(json, type);
            return list;
        } catch (Exception e) {
            e.printStackTrace();
        }  

        return list;
    }
}