给JavaBean赋默认值并且转Json字符串的实例

package com.up.util.tools; 
import com.Google.gson.Gson; 
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
 

public class JavaBeanToJson {
    public static String toJson(Class clazz) throws Exception {
        Gson gson = new Gson();
        String result = "";
        if (clazz.equals(Map.class)) {
            result = clazz.getName() + "\t" + gson.toJson(new HashMap<>());
        } else {
            Object object = clazz.newInstance();
            object = getBean(object);
            result = clazz.getName() + "\t" + gson.toJson(object);
        }
        return result;
    }
 
    private static <T> Object getBean(T object) throws Exception {
        Class<?> classType = object.getClass();
        //sqlRowSet srs = jdbcTemplate.queryForRowSet(sql);
        Field[] fields = classType.getDeclaredFields();//得到对象中的字段
        //每次循环时，重新实例化一个与传过来的对象类型一样的对象
        T objectCopy = (T) classType.getConstructor(new Class[]{}).newInstance(new Object[]{});
        for (int i = 0; i < fields.length; i++) {
            Field field = fields[i];
            String fieldName = field.getName();
            Object value = null;
            //根据字段类型决定结果集中使用哪种get方法从数据中取到数据
            if (field.getType().equals(String.class)) {
                value = "";
            } else if (field.getType().equals(int.class) || field.getType().equals(Integer.class)) {
                value = new Integer(0);
            } else if (field.getType().equals(double.class) || field.getType().equals(Double.class)) {
                value = new Double(0);
            } else if (field.getType().equals(long.class) || field.getType().equals(Long.class)) {
                value = new Long(0);
            } else if (field.getType().equals(Date.class)) {
                value = new Date();
            } else if (field.getType().equals(Object.class)) {
                value = new Object();
            }
            // 获得属性的首字母并转换为大写，与setXXX对应
            String firstLetter = fieldName.substring(0, 1).toUpperCase();
            String setMethodName = "set" + firstLetter
                    + fieldName.substring(1);
            if (fieldName.equals("serialVersionUID")) {
                continue;
            }
            Method setMethod = classType.getMethod(setMethodName,
                    new Class[]{field.getType()});
            setMethod.invoke(objectCopy, new Object[]{value});//调用对象的setXXX方法
        } 
        return objectCopy;
    }
}

<!--jackson 2.x版本依赖-->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.8.1</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.8.6</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.8.6</version>
</dependency>
<!--junit依赖-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

package com.john.json; 
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test; 
import java.io.IOException; 
public class TestJackson {
 
    @Test
    public void testObjAndJson() throws IOException { 
        Dog dog = new Dog();
        dog.setName("樱桃");
        dog.setAge(1);
        dog.setFood("小米");
 
        //创建Jackson高级对象
        ObjectMapper mapper = new ObjectMapper();
 
        //对象转换为对应的json格式字符串
        String json = mapper.writeValueAsString(dog); 
        System.out.println(json);
 
        //json格式字符串转换为对应的对象
        Dog dogBack = mapper.readValue(json, Dog.class); 
        System.out.println(dogBack.getName()+"--"+dogBack.getAge()+"--"+dogBack.getFood()); 
    }
}

<!--gson依赖-->
<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.2.4</version>
</dependency>
<!--junit依赖-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

package com.john.json; 
import com.google.gson.Gson;
import org.junit.Test; 
public class TestGson {
 
    @Test
    public void testObjAndJson() { 
        Dog dog = new Dog();
        dog.setName("妞妞");
        dog.setAge(3);
        dog.setFood("大米");
 
        //创建gson对象
        Gson gson = new Gson();
 
        //对象转化为对应的json格式字符串
        String dogJson = gson.toJson(dog); 
        System.out.println(dogJson);
 
        //json格式字符串转换为对应的对象
        Dog dogBack = gson.fromJson(dogJson, Dog.class); 
        System.out.println(dogBack.getName()+"--"+dogBack.getAge()+"--"+dogBack.getFood());
    } 
}