试验一下

类图

po类

public class C3 {

    private C1 c1;
    private C2 c2;

    public C1 getC1() {
        return c1;
    }

    public void setC1(C1 c1) {
        this.c1 = c1;
    }

    public C2 getC2() {
        return c2;
    }

    public void setC2(C2 c2) {
        this.c2 = c2;
    }

    @Override
    public String toString() {
        return "C3{" +
                "c1=" + c1 +
                ",c2=" + c2 +
                '}';
    }
}

2. C1

public class C1 {

    private String a1;
    private List<C4> c4 = new ArrayList<>();

    public List<C4> getC4() {
        return c4;
    }

    public void setC4(List<C4> c4) {
        this.c4 = c4;
    }

    public String getA1() {
        return a1;
    }

    public void setA1(String a1) {
        this.a1 = a1;
    }

    @Override
    public String toString() {
        return "C1{" +
                "a1='" + a1 + '\'' +
                ",c4=" + c4 +
                '}';
    }
}

3. C2

public class C2 {

    private String a2;

    public String getA2() {
        return a2;
    }

    public void setA2(String a2) {
        this.a2 = a2;
    }

    @Override
    public String toString() {
        return "C2{" +
                "a2='" + a2 + '\'' +
                '}';
    }
}

4. C4

public class C4 {

    private String a4;

    public String getA4() {
        return a4;
    }

    public void setA4(String a4) {
        this.a4 = a4;
    }

    @Override
    public String toString() {
        return "C4{" +
                "a4='" + a4 + '\'' +
                '}';
    }
}

测试类

@Test
    public void testFastJson(){        
        String s = "{\"c1\":{\"a1\":\"1\",\"c4\":[{\"a4\":\"4\"},{\"a4\":\"5\"}]},\"c2\":{\"a2\":\"3\"}}".trim();
        C3 c3 = JSON.parSEObject(s,C3.class);
        System.out.println(c3);
    }

可以解析

注意两点：

1. 类的成员的命名要与json中对应的“对象/数组”名称一致

2. 嵌套成内部类也是可以解析的，参考：fastjson可以解析嵌套的内部类吗？

可以说fastjson还是很强大的