在某些情况下我们希望JSON按照一个比较友好的格式换行输出，不要都挤在一起，可以使用JACKSON实现。

• 引入Jackson

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.5</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.5</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.9.5</version>
</dependency>

• 格式化输出测试

public class JacksonTest {
    @Test
    public void test1() throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        List list = new ArrayList<>();
        Map map1 = new HashMap<>();
        map1.put("id","111");
        map1.put("users", Arrays.asList(1,2,3,4,5,5));
        list.add(map1);
        Map map2 = new HashMap();
        map2.put("name","zqw");
        list.add(map2);
        //普通输出
        System.out.println(mapper.writeValueAsString(list));
        //格式化/美化/优雅的输出
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(list));


        String str = "[ {\n" +
                "  \"id\" : \"111\",\n" +
                "  \"users\" : [ 1, 2, 3, 4, 5, 5 ]\n" +
                "}, {\n" +
                "  \"name\" : \"zqw\"\n" +
                "} ]";
        Object obj = mapper.readValue(str, Object.class);
        System.out.println(mapper.writeValueAsString(obj));
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj));
    }
}