Java链式方法调用

经常会看到一些代码使用连续的.set()方法来进行初始化，这种实现方式是链式方法调用。

传统方式

通常，我们在进行对象初始化的时候，可以调用.set()方法对某个属性进行赋值，例如：

public class FixedDepositDetails {
    private long id;
    private float depositAmount;
    private int tenure;
    private String email;
    
    public FixedDepositDetails() {
    }

    public FixedDepositDetails(long id, float depositAmount, int tenure, String email) {
        this.id = id;
        this.depositAmount = depositAmount;
        this.tenure = tenure;
        this.email = email;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public float getDepositAmount() {
        return depositAmount;
    }

    public void setDepositAmount(float depositAmount) {
        this.depositAmount = depositAmount;
    }

    public int getTenure() {
        return tenure;
    }

    public void setTenure(int tenure) {
        this.tenure = tenure;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "FixedDepositDetails{" +
                "id=" + id +
                ", depositAmount=" + depositAmount +
                ", tenure=" + tenure +
                ", email='" + email + '\'' +
                '}';
    }
}

使用方式也是传统的方法，例如：

import org.junit.Test;

public class FixedDepositDetailsTest {
    @Test
    public void testObjectCreate() {
        FixedDepositDetails fixedDepositDetails = new FixedDepositDetails();
        fixedDepositDetails.setId(1L);
        fixedDepositDetails.setDepositAmount(1000);
        fixedDepositDetails.setEmail("[email protected]");
        fixedDepositDetails.setTenure(100);
        System.out.println(fixedDepositDetails);
    }
}

没有什么特别的，这是大家都熟悉的模式。

链式方法

现在，来看一下，链式调用，其代码如下：

import org.junit.Test;

public class FixedDepositDetailsTest {
    @Test
    public void testObjectCreate() {
        FixedDepositDetails fixedDepositDetails = new FixedDepositDetails();
        fixedDepositDetails.setId(1L)
        	.setDepositAmount(1000)
        	.setEmail("[email protected]")
        	.setTenure(100);
        System.out.println(fixedDepositDetails);
    }
}

是不是和前面创建对象的方式有很大不同。
要实现链式方法调用，其实很简单，就是让每个set方法，返回自己即可，也很容易实现，例如：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class FixedDepositDetails {
    private static Logger logger = LoggerFactory.getLogger(FixedDepositDetails.class);
    private long id;
    private float depositAmount;
    private int tenure;
    private String email;

    public FixedDepositDetails() {
        logger.info("Created instance");
    }

    public long getId() {
        return id;
    }

    public FixedDepositDetails setId(long id) {
        this.id = id;
        return this;
    }

    public float getDepositAmount() {
        return depositAmount;
    }

    public FixedDepositDetails setDepositAmount(float depositAmount) {
        this.depositAmount = depositAmount;
        return this;
    }

    public int getTenure() {
        return tenure;
    }

    public FixedDepositDetails setTenure(int tenure) {
        this.tenure = tenure;
        return this;
    }

    public String getEmail() {
        return email;
    }

    public FixedDepositDetails setEmail(String email) {
        this.email = email;
        return this;
    }

    public String toString() {
        return "id :" + id + ", deposit amount : " + depositAmount
                + ", tenure : " + tenure + ", email : " + email;
    }
}

idea自动生成

可以使用idea环境，自动生成返回this的set方法，选择Setter template:为Builder即可生成想要的set方法，如下图所示：

当然，不管哪种方式，都是可以的。