fastxml 简单常用注解学习笔记

fastxml 简单常用注解学习笔记

@JsonNaming

@JsonIgnoreProperties

@JsonIgnore

@JsonFormat

@JsonDeserialize

@JsonSerialize

@JsonProperty

如下User类

package com.usoft;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonNaming;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

import java.math.BigDecimal;
import java.util.Date;

/**
 * Created by xinxingegeya on 2015/3/7.
 */
@JsonNaming(PropertyNamingStrategy.LowerCaseWithUnderscoresStrategy.class)
@JsonIgnoreProperties(value = {"enabled", "age", "bigDecimal"}, ignoreUnknown = true)
public class User {

    private String username;
    @JsonIgnore
    private String passwd;
    @JsonFormat(pattern = "yyyy-MM-dd")
    @JsonDeserialize(using = CustomDateDeserialize.class)
    private Date createDate;
    private boolean enabled;
    private int age;
    private BigDecimal bigDecimal;
    @JsonSerialize(using = CustomDoubleSerialize.class)
    private double helloDouble;
    // 该属性没有setter和getter方法，如果想要序列化必须标注该注解
    @JsonProperty(value = "belong_to_role")
    private boolean belongToRole = false;

    public double getHelloDouble() {
        return helloDouble;
    }

    public void setHelloDouble(double helloDouble) {
        this.helloDouble = helloDouble;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPasswd() {
        return passwd;
    }

    public void setPasswd(String passwd) {
        this.passwd = passwd;
    }

    public Date getCreateDate() {
        return createDate;
    }

    public void setCreateDate(Date createDate) {
        this.createDate = createDate;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public BigDecimal getBigDecimal() {
        return bigDecimal;
    }

    public void setBigDecimal(BigDecimal bigDecimal) {
        this.bigDecimal = bigDecimal;
    }
}

相关的类

package com.usoft;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CustomDateDeserialize extends JsonDeserializer<Date> {

    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

    @Override
    public Date deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
        Date date = null;
        try {
            date = sdf.parse(jp.getText());
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }
}

package com.usoft;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

import java.io.IOException;
import java.text.DecimalFormat;

public class CustomDoubleSerialize extends JsonSerializer<Double> {

    private DecimalFormat df = new DecimalFormat("##.00");

    @Override
    public void serialize(Double value, JsonGenerator jgen,
                          SerializerProvider provider) throws IOException {
        jgen.writeString(df.format(value));
    }
}

测试类，

package com.usoft;

import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.math.BigDecimal;
import java.util.Date;

/**
 * Created by xinxingegeya on 2015/3/7.
 */
public class TestJson {
    private static final JsonMapper mapper = new JsonMapper();
    private static Logger logger = LoggerFactory.getLogger(TestJson.class);

    /**
     * fastxml序列化json
     */
    @Test
    public void test76() {
        User user = new User();
        user.setAge(19);
        user.setBigDecimal(new BigDecimal(12));
        user.setCreateDate(new Date());
        user.setEnabled(true);
        user.setPasswd("122");
        user.setUsername("admin");
        user.setHelloDouble(3.1);

        String json = mapper.toJson(user);
        logger.info(json);
    }

    @Test
    public void testu68() {
        String helloJson = "{"username":"admin","passwd":"122","createDate":"2015-03-07 13:25:47","birthday":"2015-03-07 13:25:47"}";
        User user = mapper.fromJson(helloJson, User.class);
        logger.info(user.toString());
        logger.info(user.getCreateDate().toString());
    }
}

更多详见：http://blog.csdn.net/sdyy321/article/details/40298081

最后附上一个Json序列化的工具类，该工具类是从springside项目中拿来的。

package com.usoft;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.util.JSONPObject;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.text.SimpleDateFormat;

public class JsonMapper {

    private static Logger logger = LoggerFactory.getLogger(JsonMapper.class);

    private ObjectMapper mapper;

    public JsonMapper() {
        this(null);
    }

    public JsonMapper(JsonInclude.Include include) {
        this.mapper = new ObjectMapper();
        //设置日期格式当使用jackson在处理时间时，默认是将时间输出为timestamps格式
        SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        this.mapper.setDateFormat(fmt);
        //设置输出时包含属性的风格
        if (include != null) {
            this.mapper.setSerializationInclusion(include);
        }
        //设置输入时忽略在JSON字符串中存在但Java对象实际没有的属性
        this.mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
    }

    //Include.Include.ALWAYS 默认
    //Include.NON_DEFAULT 属性为默认值不序列化
    //Include.NON_EMPTY 属性为 空（“”）  或者为 NULL 都不序列化
    //Include.NON_NULL 属性为NULL 不序列化

    /**
     * 属性为 空（“”） 或者为 NULL 都不序列化
     *
     * @return
     */
    public static JsonMapper nonEmptyMapper() {
        return new JsonMapper(JsonInclude.Include.NON_EMPTY);
    }

    /**
     * 属性为默认值不序列化
     *
     * @return
     */
    public static JsonMapper nonDefaultMapper() {
        return new JsonMapper(JsonInclude.Include.NON_DEFAULT);
    }

    /**
     * 属性为NULL不序列化
     *
     * @return
     */
    public static JsonMapper nonNullMapper() {
        return new JsonMapper(JsonInclude.Include.NON_NULL);
    }

    /**
     * Object可以是POJO，也可以是Collection或数组。
     * 如果对象为Null, 返回"null".
     * 如果集合为空集合, 返回"[]".
     *
     * @param object
     * @return
     */
    public String toJson(Object object) {

        try {
            return this.mapper.writeValueAsString(object);
        } catch (IOException e) {
            JsonMapper.logger.warn("write to json string error:" + object, e);
            System.out.println(e.getMessage());
            return null;
        }
    }

    /**
     * 反序列化POJO或简单Collection如List<String>.
     * <p/>
     * 如果JSON字符串为Null或"null"字符串, 返回Null. 如果JSON字符串为"[]", 返回空集合.
     * <p/>
     * 如需反序列化复杂Collection如List<MyBean>, 请使用fromJson(String,JavaType)
     *
     * @param jsonString
     * @param clazz
     * @return
     * @see #fromJson(String, com.fasterxml.jackson.databind.JavaType)
     */
    public <T> T fromJson(String jsonString, Class<T> clazz) {
        if (StringUtils.isEmpty(jsonString)) {
            return null;
        }

        try {
            return this.mapper.readValue(jsonString, clazz);
        } catch (IOException e) {
            JsonMapper.logger.warn("parse json string error:" + jsonString, e);
            return null;
        }
    }

    /**
     * 反序列化复杂Collection如List<Bean>, 先使用函數createCollectionType构造类型,然后调用本函数.
     *
     * @param jsonString
     * @param javaType
     * @return
     * @see #createCollectionType(Class, Class...)
     */
    public <T> T fromJson(String jsonString, JavaType javaType) {
        if (StringUtils.isEmpty(jsonString)) {
            return null;
        }

        try {
            return (T) this.mapper.readValue(jsonString, javaType);
        } catch (IOException e) {
            JsonMapper.logger.warn("parse json string error:" + jsonString, e);
            return null;
        }
    }

    /**
     * 構造泛型的Collection Type如:
     * ArrayList<MyBean>,
     * 则调用constructCollectionType(ArrayList.class,MyBean.class)
     * HashMap<String,MyBean>, 则调用(HashMap.class,String.class, MyBean.class)
     *
     * @param collectionClass
     * @param elementClasses
     * @return
     */
    public JavaType createCollectionType(Class<?> collectionClass,
                                         Class<?>... elementClasses) {
        return this.mapper.getTypeFactory().constructParametricType(
                collectionClass, elementClasses);
    }

    /**
     * @param jsonString
     * @param object
     * @return
     */
    public <T> T update(String jsonString, T object) {
        try {
            return (T) this.mapper.readerForUpdating(object).readValue(
                    jsonString);
        } catch (JsonProcessingException e) {
            JsonMapper.logger.warn("update json string:" + jsonString
                    + " to object:" + object + " error.", e);
        } catch (IOException e) {
            JsonMapper.logger.warn("update json string:" + jsonString
                    + " to object:" + object + " error.", e);
        }
        return null;
    }

    /**
     * @param functionName
     * @param object
     * @return
     */
    public String toJsonP(String functionName, Object object) {
        return this.toJson(new JSONPObject(functionName, object));
    }

}

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